“Is this the greatest concert any of us have ever heard?” Robert Downey Jr. asked from the stage of the Beacon Theater in Manhattan on Monday night. The crowd roared in agreement.

The lineup already featured Deborah Harry, Darryl McDaniels (of Run D.M.C.), James Taylor, Shaggy and Ricky Martin. Yet to come were Bruce Springsteen and John Mellencamp, who would perform duets of “Pink Houses” and “Glory Days,” and a reunion of Annie Lennox and Dave Stewart of the Eurythmics.

The remarkable bill was put together by Sting and his wife, Trudie Styler, to benefit the Rainforest Fund, the conservation group they founded 30 years ago, when MTV videos helped to usher in Band AID, Live AID and other forms of music activism. Those videos played behind many of the acts.

“Welcome to Boomerstock,” Bob Geldof said, where “guys and gals with guitars and keyboards still think it’s possible to change things.” He performed his 1979 hit, “I Don’t Like Mondays,” a song, he noted, he was more than a little “sick of.”

After Sting performed “Englishman in New York,” as well as a cover of “Sledgehammer” by Peter Gabriel, the hurricane of the talent swept into the Mandarin Oriental Hotel on Columbus Circle for an after-party. They were joined by Chazz Palminteri, Karlie Kloss, Donna Karan and Val Kilmer, who at one point during dinner fell off his chair.

“There’s something about the community in this show between the artists and the audience that creates some kind of magic,” said Sting, who was holding court in a corner.

But he lamented the state of affairs for rainforests, especially in Brazil where deforestation has accelerated under President Jair Bolsonaro.

“This is the most profound existential crisis in history, but our leaders have to get on board,” he said. “We can’t tolerate it anymore.”

Chanel Christmas

Lily-Rose Depp was shivering when she stepped onto the red carpet at a Chanel No. 5 L’Eau event at the Standard, High Line hotel on Tuesday night, lashed by a frigid wind.

“I grew up in California so I’m not as used to the cold weather,” said Ms. Depp, who wore a tight black top and mid-thigh skirt. “I’m a little chilly right now, but I like the cold. Snow is really neat to me.”

Standing next to her was Zosia Mamet, who was enduring the cold snap a little better. “I grew up half in L.A., and Christmas in L.A. just feels wrong,” she said. “There are palm trees lit up, and it’s 70 degrees.”

In New York, Ms. Mamet added, “there are lights and music everywhere. It feels like the holiday is so embraced.”

The fashionable crowd included Kacey Musgraves, Soo Joo Park, Ella Hunt, Jemima Kirke, Diane Kruger and her boyfriend, Norman Reedus. Black-clad male models stood next to a small skating rink (free to the public through Sunday), waiting like winter lifeguards.

But it was too cold to skate, so guests mostly stayed inside, where Monsta X, the K-pop band, performed three of their hits. Its five young members were nothing if not on message.

“Chanel No. 5 has always been No. 1 for us,” said I.M., the group’s lead rapper.

Asked if they would be looking for Christmas presents while visiting New York, Kihyun, a lead vocalist, pointed to the Chanel watch on his wrist, a gift from their hosts.

“Watches,” I.M. said. “We already got it.”