A landmark antitrust trial against Google concluded on Friday after a federal judge heard final arguments, setting the stage for a ruling that could fundamentally shift the tech industry’s power.

“The importance and significance of this case is not lost on me, not only for Google but for the public,” Judge Amit P. Mehta said in the final moments of the proceedings on Friday. He thanked the lawyers who argued the case, and then added, “I guess you’ve passed the baton to us.”

Now, he must decide the case in which the Justice Department and state attorneys general say that Google has abused a monopoly over the search business, stifling competitors and limiting innovation, something the company denies.

During two days of closing arguments, Judge Mehta of the U.S. District Court for the District of Columbia did not reveal how he planned to rule. He grilled both sides, frequently referencing testimony and evidence from the 10-week trial last year to poke holes in their arguments. He also demanded that they explain how their positions fit with major legal precedents.

As the proceedings closed on Friday, Kenneth Dintzer, the Justice Department’s lead trial lawyer, argued that if antitrust laws “cannot thaw” a search business dominated by Google, the company’s practices will continue into the future.

John E. Schmidtlein, Google’s lead lawyer, countered that a ruling in favor of the government “would be an unprecedented decision to punish a company for winning on the merits.”

Judge Mehta’s ruling in the coming weeks or months will probably influence the course of other government antitrust lawsuits against Apple, Amazon and Meta, the owner of Instagram and WhatsApp, as U.S. regulators try to rein in their power.

The government argues Google illegally cemented a monopoly in search by paying Apple and other tech partners billions of dollars to feature the Google search engine in their products.

On Friday, the discussion focused on the government’s second claim that the company also has a monopoly over the ads that run in search results.

Google pointed to other companies that compete in search and advertising.

“Facebook, Instagram, TikTok, Amazon — all of these companies have very, very detailed and very useful information that allows them to give advertisers lots and lots of different options to reach the consumer groups they’re most interested in,” Mr. Schmidtlein argued.

Judge Mehta asked the Justice Department, to explain why search ads were so different from ads on Facebook and other social platforms.

“How does that measure up with reality?” he asked. “It can’t be that Facebook’s ad platform is an inferior product and they’re making billions of dollars.”

Judge Mehta also mentioned the success of TikTok, which, he said, had a “pretty good ad platform” and was growing. He said he had spent some time using TikTok’s search to research the case.

In a seeming nod to national security concerns about that app, he added: “Not that I have it on my phone, just to be clear.”

The government also said the judge should sanction Google for a company policy that automatically turned off the history for workplace chats, arguing that the policy resulted in the destruction of evidence. Mr. Dintzer said the court needed to “say this is wrong” to stop Google from hiding evidence in the future. A lawyer for Google, Colette T. Connor, denied the company had done anything inappropriate.

“Let me just be perfectly candid,” Judge Mehta said. “Google’s document retention policy leaves a lot to be desired.”

Although the Met Gala serves as a branding event for Vogue, it has long accepted sponsorships from the tech giants that have threatened the very survival of legacy media publications.

Jeff Bezos, the Amazon founder, appeared as the ball’s honorary chair in 2012. Four years later, when Apple was a Met Gala sponsor, its chief executive, Tim Cook, showed up in tux and tails. And Instagram supplied cash in 2022.

The 2024 event is sponsored, in part, by TikTok, the social media goliath whose future looks murkier than that of Condé Nast, the publisher of Vogue, The New Yorker and other magazines, which has laid off employees and shuttered or sold off some of its publications in recent years.

TikTok found itself in jeopardy last month, when President Biden signed a bill that gave ByteDance, the Chinese company that owns TikTok, nine months to sell off the app or face a ban in the United States. In the wake of that political firestorm, Shou Chew, the 41-year-old chief executive of TikTok, is expected to join dozens of celebrity guests at the Metropolitan Museum of Art in Manhattan on Monday evening.

He was selected by Anna Wintour as an honorary chair for the benefit, which raises tens of millions of dollars each year for the museum’s Costume Institute. Ms. Wintour, the global editorial director of Condé Nast and the editor in chief of Vogue, has run the event for a quarter of a century, using her sense of celebrity and fashion synergy to create a splashy showcase of some of the world’s most influential people, a group that has come to include more social media influencers and fewer one-name stars (Beyoncé, Lady Gaga, Madonna) in recent years.

TikTok may be loathed by Washington lawmakers who have raised concerns about the Chinese government’s access to its 170 millions users in the United States, but it remains an undeniable cultural force in American life, especially among Gen Z. The app is also a fashion force, and the Met Gala provides many TikTok creators with plenty of fodder. That makes the little-known Mr. Chew at least as powerful as the much more recognizable co-chairs of this year’s party — Zendaya, Jennifer Lopez, Bad Bunny, Chris Hemsworth and Ms. Wintour herself.

Along with TikTok, the luxury fashion brand Loewe is a sponsor; its creative director, Jonathan Anderson, will serve alongside Mr. Chew as an honorary chair.

TikTok declined to reveal its financial contribution to the star-studded event. In previous years, a sponsor is known to have kicked in roughly $5 million.

Mr. Bezos and Mr. Cook were known quantities when they greeted the likes of Rihanna and Beyoncé at previous Met Galas. Mr. Chew, on the other hand, is likely to go unrecognized by most of the gawkers who line up behind the barricades along Fifth Avenue, many of whom may be making TikTok videos on their phones.

A Charm Offensive

Starting in 2022, when U.S. lawmakers were turning up the heat on TikTok, the company changed its public relations strategy. Instead of keeping a low profile, it embarked on a charm offensive, with the fresh-faced Shou (pronounced “show”) Chew front and center.

As TikTok plowed millions into its lobbying efforts, Mr. Chew met with the heads of think tanks in Washington and global leaders at the World Economic Forum in Davos, Switzerland. At The New York Times’s DealBook conference in November 2022, he fielded questions about national security concerns while wearing jeans, a casual blue blazer over a white T-shirt, and white sneakers that looked fresh out of the box.

His expected appearance at the Met Gala — once a staid affair for New York blue bloods that has become an East Coast Oscars on Ms. Wintour’s watch — can be viewed as part of TikTok’s shift in how it presents itself to the public. But this time around, instead of sitting down with those who have influence over matters of policy, the TikTok chief will be standing on a red carpet before a squadron of photographers.

Mr. Chew, who declined through a TikTok representative to be interviewed for this article, grew up in Singapore. That is where he has his main residence with his wife, Vivian Kao, 42, a onetime Goldman Sachs associate, and their three children. In 2021, the couple spent more than $60 million on a house in the Queen Astrid Park area of the island nation, according to The Business Times of Singapore.

The family is intensely private. A rare glimpse of Ms. Kao and one of their children appeared in a video that Mr. Chew posted on TikTok from a recent Taylor Swift concert at Singapore National Stadium.

Mr. Chew has said that his father worked in construction and that his mother was a bookkeeper. After attending one of Singapore’s top secondary schools, he completed two years of mandatory national service in the Singapore Armed Forces, where he was an officer. From there, he enrolled at University College London.

After graduating in 2006 with a degree in economics, he took a job in the London office of Goldman Sachs. That was where he met Nathalie du Preez, who remains a friend of his.

“We sat on the same floor, and he was walking past,” Ms. du Preez recalled in a phone interview.

In an early conversation, they found that they had both applied to Harvard Business School. They took coffee breaks together at Leonidas Chocolates around the corner from the office.

When they arrived at Harvard in the fall of 2008, Ms. du Preez and Mr. Chew shared a ride with a group of people bound for Ikea. They were just two of the many students on the lookout for reasonably priced home décor items.

“He’s come a long way since then,” she said.

Ms. du Preez and several other Harvard Business School classmates interviewed for this article recalled Mr. Chew as someone who was funny, although they could not recall a specific funny thing he had said. They also agreed that he was razor-sharp, but offered no particular examples of his acuity.

They described him as curious about pop culture and sports, saying he was a fan of Manchester United and recalling that he had attended a David Guetta show at the Roxy in Boston. They mentioned that he liked video games, including the soccer game FIFA, and noted that he was the tidiest of his roommates.

Mr. Chew met the woman who would become his wife, Ms. Kao, when they were both at Harvard Business School. A graduate of Wellesley College, she had grown up in Bethesda, Md., and is Taiwanese American.

Mr. Chew and Ms. Kao found themselves in business school as the financial crisis arrived. “We called it the ‘just in time’ admissions class, because the markets crashed that fall,” Caren Kelleher, a fellow classmate, said in an interview.

Although it was a time when big banks were failing, some of Mr. Chew’s fellow business students were surprised when he took a summer internship at Facebook, rather than going into finance. The social media company was only five years old and years away from going public.

His classmates later realized he had made a prescient choice, according to Jean Abillama, who lived across the street from Mr. Chew in Cambridge, Mass. “He was seeing this big wave of tech and e-commerce, the tech wave coming to light,” she said.

Master’s degree in hand, he joined DST Global, a venture capital firm led by Yuri Milner, a Russian billionaire who was on his way to becoming one of the most important private investors in Silicon Valley companies. Mr. Chew served as Mr. Milner’s point man in China, where he helped lead investments in Alibaba and the Chinese ride-sharing service DiDi.

During that time, Mr. Milner provided a reported $10 million in financing to a news-aggregation app founded by the entrepreneur Zhang Yiming, who developed a rapport with Mr. Chew. The app would become ByteDance. Mr. Chew also helped with DST Global’s investment in Xiaomi, one of China’s largest phone manufacturers.

In 2013, Mr. Chew and Ms. Kao were married. Two years later, Mr. Chew left DST to become the chief financial officer of Xiaomi, which he helped take public in 2018.

He Got the Job

Mr. Chew was named the chief financial officer of ByteDance in March 2021. He ascended to the top TikTok job two months later. In November of that year, he stepped down as ByteDance’s chief financial officer.

TikTok’s previous chief executive, Kevin Mayer, had resigned after less than four months on the job, citing the increasing pressure put on the company by the Trump administration because of its ties to China.

The opposition of U.S. lawmakers did not abate during the presidency of Joseph R. Biden Jr. As Mr. Chew worked to keep lawmakers at bay, he found time to attend the 2022 Met Gala with Ms. Kao. He went all-out formal, in traditional white tie and tails; she wore a resplendent floral-patterned gown.

Nowadays, Ms. Kao runs Tamarind Global, a family office that, according to its website, “manages investments and philanthropy” for a “Singaporean family.” Its shareholders include Mr. Chew and a trust linked to Mr. Chew and Ms. Kao, according to public records.

There has been debate about whether Mr. Chew — who travels with a small security detail — is the controlling force at TikTok. Company sources have told The Times that major strategic decisions were handled by Mr. Yiming, among others.

Mr. Chew displayed a sense of fun in his TikTok handle — @shou.time — which riffs on the pronunciation of his first name. But the account did not have much of a following until March 2023, when he was grilled by Congress.

Under aggressive questioning, Mr. Chew was made to repeat that he was a citizen of Singapore, not China. He went on to stress that TikTok was not controlled by the Chinese Communist Party and noted that his wife is an American, telling his questioners, “By the way, she was just born a few miles away from here.”

That was the appearance that catapulted him into public consciousness. Before the hearing, he had fewer than 20,000 TikTok followers. He now has 3.9 million.

Users posted clips highlighting belligerent questions from lawmakers. A number of TikTokers even called Mr. Chew “zaddy,” a slang term that refers to an older, attractive man.

On Nov. 8, 2023, TikTok announced that it would serve as “the lead sponsor” of this year’s Metropolitan Museum of Art Costume Institute Benefit, the formal name of the Met Gala. Days after the announcement, Vogue Singapore published a rare sit-down interview with Mr. Chew.

He was photographed in Louis Vuitton jeans and a velvet Brunello Cucinelli blazer, and he spoke benignly about his mandatory service in Singapore’s armed forces in “the jungles of Brunei” and doing diaper duty for a third time. “There’s quite an age gap between this kid and the previous kid,” he said in the interview. “My wife and I are relearning everything, like changing diapers.”

Along with other top tech executives, Mr. Chew was called before Congress again in January. He stressed that he did not live in China and said he was not a member of the Chinese Communist Party.

While turning down interview requests from news organizations digging into TikTok’s Chinese ties, Mr. Chew gave an interview to another Condé Nast publication, Wired, during a TikTok music festival in Mesa, Ariz., in December 2023.

The Wired article largely kept the focus on TikTok’s pop-culture footprint while seeming to defend it against its American critics by arguing that “a thinly veiled anti-Chinese xenophobia has become a reliable part of the U.S. political playbook.” It also included an advance plug for Mr. Chew’s appearance at the Met Gala.

“It’s very cultural,” Mr. Chew told Wired. “Fashion is an incredibly important part of TikTok. Louis Vuitton has 12 million followers on our app.” (The fashion house now has more than 13 million TikTok followers.)

Ms. du Preez, the Goldman Sachs colleague and Harvard classmate, said she was not surprised that Mr. Chew would be interested in teaming up with Vogue and Ms. Wintour, particularly at a time when the company he leads is trying to show that it is not controlled by China.

“The Met Gala is an incredibly well-followed evening,” she said. “In terms of making friends in the U.S., I think it would make sense to do that, and everyone who is going will have a TikTok account.”

Not that she expected him to pick out a memorable ensemble.

“I have no doubt Vivian will dress him in something beautiful,” Ms. du Preez said. “And at this point he can get a lot of advice from anyone about what to wear. I’m sure Anna Wintour can give him tips.”

For the record, Mr. Chew is slated to wear something from Ralph Lauren, the American designer whose fondness for red, white and blue has made him a natural choice to outfit U.S. Olympics teams in patriotic garb.

Ryan Mac contributed reporting. Kirsten Noyes contributed research.