BTS Took Center Stage at the U.N. Over One Million Fans Watched Live.

Amid the clutches of a pandemic, the conflict in Afghanistan and deadly storms exacerbated by climate change, more than 1 million people were transfixed by the United Nations on Monday. Not to watch a head of state, but rather a boy band: BTS.

The seven members of the Korean pop group, a multibillion-dollar act known for its dynamic dance moves, catchy lyrics and frenzied fans, promoted the coronavirus vaccine and lauded young people for their resiliency during a nearly seven-minute speech at the U.N. headquarters in New York.

The band’s appearance came one day before more than 100 world leaders and representatives are to gather on Tuesday for the opening of the General Assembly, an annual conclave that was held mostly virtually last year because of the pandemic.

Accompanying President Moon Jae-in of South Korea, who designated them as special presidential envoy for future generations and culture, the band then showed a prerecorded video of their hit song “Permission to Dance.”

The video showed the young crooners dancing in the empty aisles of the Assembly Hall — where presidents and autocrats have lobbed threats of annihilation and diplomats have staged walkouts — and later outside the complex.

The band’s legion of fans followed along intently on the U.N.’s YouTube channel, flooding a live chat with gushing messages, many with purple heart emojis that have become a calling card.

“I’ve heard that people in their teens and 20s today are being referred to as Covid’s lost generation,” said Kim Nam-joon, the band’s lead singer, who performs under the stage name RM (formerly Rap Monster). “But I think it’s a stretch to say they’re lost just because the path they tread can’t be seen by grown-up eyes.”

Mr. Moon introduced the band’s members inside the cavernous hall, where the group wore dark suits, lanyards with name tags and lapel pins promoting the U.N.’s Sustainable Development Goals campaign.

He said that BTS, whose name is an abbreviation of the Korean words Bangtan Sonyeondan, or Bulletproof Boy Scouts, was “probably the artist that is most loved by people around the world.”

It was not the first time that the band, a dominant force in the Korean pop music space known as K-pop, had appeared at the United Nations. In 2018, BTS visited the U.N. to help UNICEF promote Generation Unlimited, a campaign dedicated to educating young people and providing them vocational training.

On Monday, a livestream of the band’s appearance on the U.N.’s YouTube channel racked up about one million views. Later in the day, the view count surpassed six million.

J-hope, one of the band’s members, said that there had been substantial speculation about whether the group had been vaccinated. All seven singers have been vaccinated, he said.

“What is important are the choices we make when we’re faced with change, right?” he said. “Of course, we received vaccinations. The vaccination was a sort of ticket to meeting our fans waiting for us and to being able to stand here before you today.”