The Met Gala Comes to Jesus. Rihanna Comes as the Pope.

NEW YORK — Each spring, a gala serves as the opening of the annual blockbuster show at the Metropolitan Museum’s Costume Institute. Hundreds of celebrities arrive in a frantic seasonal migration for that party.

This year, that exhibition is “Heavenly Bodies: Fashion and the Catholic Imagination” — and the choice of a religious theme gave a number of gala attendees a hot chance to tee off to the line of reporters on the event’s packed red carpet on Monday night.

“I’m a pagan,” said actress Frances McDormand. “Aren’t you?”

“This is like my skin, I’m proud to be in it,” said Lena Waithe, the actress and writer, who was regally dressed in a black suit and cape that became a broad rainbow. “I’ve got the community on my back to make sure they know I’ve got them all the time.”

“The theme to me is like be yourself,” Waithe said. “You were made in God’s image, right?”

Not every outfit was political. “I’m the back wall of the Sistine Chapel,” said Ariana Grande, the singer, whose dress was a mass of papal conclave color. “I feel fairly important in this outfit, I have to say.”

Building a relationship with the Catholic Church took significant work by the Costume Institute curator Andrew Bolton. Eventually, the church lent more than 40 items to the exhibition, which encompasses an enormous 58,600 square feet and extends to the Cloisters. A papal tiara, with 18,000 diamonds, was flown to New York with a bodyguard.

The Met Gala may be the world’s fanciest party. The ceremonial red carpet procession was to be followed by cocktails, then dinner (lobster with gold flakes was on the menu), then a dessert buffet. President Donald Trump proposed to his wife, Melania, there in 2004. Tickets are $30,000, but you can’t just buy one — Anna Wintour, the artistic director of Condé Nast who is one of the chairwomen, approves attendees.

And its red carpet entrance is one of the premier showcases of celebrity brands, for musicians, actors and fashion folks alike.

“This carpet is one of the most important carpets of the year,” model Bella Hadid said.

A staff member dipped to adjust the train of designer Ariana Rockefeller, David Rockefeller Jr.'s daughter.

“Leave her alone, she’s perfect,” a photographer shouted.

“We based the dress on a tapestry from the Cloisters museum,” Ariana Rockefeller said. “And of course my great-grandfather John D. Rockefeller Jr. founded the museum, so we really wanted to incorporate family history as well as honor the theme tonight.”

Unlike in the Crusades themselves, there was very little blood shed this evening. “They had to sew me in on the way here,” said Olivia Munn, who was bleeding very slightly. Her dress was inspired by Crusade-era chain mail, by H&M.

“It’s sewn into my head,” Hadid said of her veil. She was wearing Chrome Hearts. “The things we do, darling.”

And, in what has become something of a tradition, one attendee used the night to seize attention.

While all these celebrities flirted with the theme of Catholicism this year, none took it on as fearlessly as Rihanna, a chairwoman for the event who dressed like the female pope the Vatican has never had.

Rihanna’s hat was reminiscent of the papal tiaras worn by popes from the medieval era until the mid-1960s.

Others were ready to take the evening less seriously.

Favorite part of the night? “Eating a vegan cheeseburger right before,” said poet Cleo Wade.

Eva Chen wore an outfit inspired by Joan of Arc and said the bathroom was the place to be. “The secret is that is where people are partying,” she said. “No, I’m joking.”

Where were his kids, George Clooney was asked? “They’re under the dress,” he said, waving toward the enormous train on the outfit worn by his wife, Amal, one of the event’s chairwomen.

“I forgot my ticket, do you think they’ll let me in?” asked performer Rita Ora as she approached the entrance to the Met. They might, if they know who you are!

But a feeling of religiosity did suffuse the evening.

Katy Perry arrived in enormous white feathered wings. “I feel very angelic, celestial, ethereal,” Perry said on the red carpet.

“Yeah, I love God,” said comedian Tiffany Haddish. “God love me — look at my career.”

The event is underwritten by Christine and Stephen A. Schwarzman, and by Versace. In addition to Rihanna, Wintour and Amal Clooney, Donatella Versace is also a chairwoman.

Wintour has led the gala since 1999. The event, said Michael R. Bloomberg, the former mayor of New York City, “has gotten better and better each year.”