Met Gala 2021: Rihanna, Billie Eilish, Dan Levy and more honour American fashion

After a yearlong delay due to COVID-19, this year's Met Gala kicked off Monday with a bevy of surprise superstars and a theme celebrating American fashion. 

Typically taking place on the first Monday in May, the 73rd annual exhibition was split into two parts for 2021 after its cancellation in 2020 due to the pandemic. Its theme, "In America: A Lexicon of Fashion," is Part 1 of a larger, two-part "In America" show.

Unlike past shows, this first part will last a full year, coinciding for several months with Part 2, "An Anthology of Fashion," which will open in early May — when, everyone desperately hopes, a full-sized Met Gala can be held.

In lieu of that full-sized event, Monday night's festivities kicked off with a marching band and a gymnast — and early carpet walkers in sultry, sparkly looks.

This year, the gala is co-hosted by Timothée Chalamet, Billie Eilish, Amanda Gorman and Naomi Osaka. Honorary chairs are Tom Ford and sponsor Instagram's Adam Mosseri, alongside Vogue's Anna Wintour, who has served as chair for every Met Gala since 1995.

Keke Palmer was one of the first stars to arrive, wearing a stunning, earth-tone body gown with a train by Sergio Hudson.

The designer's star rose earlier this year when he dressed both U.S. Vice-President Kamala Harris and former first lady Michelle Obama. 

Meanwhile, one of the last to arrive was superstar Rihanna and boyfriend A$ap Rocky. The two arrived fashionably late — Rihanna in a black coat dress paired with Bulgari jewels, and Rocky in a quilted look covering a more traditional tux. 

The appearance also marked their official debut as a couple since their relationship was confirmed late last year.

Dune star Timothée Chalamet turned heads with his all-white ensemble, finished by a pair of Converse high-tops. 

Chalamet has become somewhat of a force in the fashion world, lauded by numerous outlets as one of the best dressed men in Hollywood. When announcing his Met Gala hosting-duties, Vogue noted his "unexpected mix of streetwear, lack of a stylist and embrace of avant-garde labels," as setting his style choices apart. 

Singer Billie Eilish, meanwhile, stunned with a flowing gown replete with a flowing train, requiring helpers to carry and smooth it out as she entered the event.

In choosing the Oscar de la Renta-crafted dress, Eilish said she felt like "it was time" to explore a different version of femininity, diverging from her typically streetwear-inspired past outfits. 

Rap star Lil Nas X glittered in gold, showing off in a one piece suit that was only revealed under a full body cape and golden suit of armour. 

Co-chair Amanda Gorman, meanwhile, was breathtaking in custom Vera Wang, with a diamond laureate in her hair.

Gorman's dress, which included more than 3,000 hand-sewn crystals, was made to evoke a starry night sky. She told Vogue she felt like Lady Liberty, reimagined. Her crown, the star poet said, was a nod to publishing. 

The final host, Naomi Osaka, wanted to celebrate all her cultures — Japanese, Haitian and American — and picked a Louis Vuitton gown designed in collaboration with her sister, Mari Osaka.

It was a swirling blue, aqua and purple print, with long, black ruffle sleeves and a wide red sash.

A number of Canadian stars also made a splash with their fashion choices. Singer Grimes showed up in a Dune-inspired dress, Elliot Page modelled a simple, tie-less black suit and Schitt's Creek actor Dan Levy shocked in a blue confection from Loewe.

It had, according to the brand, "printed leg of mutton sleeves" on a polo shirt with an appliqué of two men kissing.

Not to be upstaged, Canadian designer Aurora James posed with U.S. Rep. Alexandria Ocasio-Cortez and the "tax the rich" dress she designed — an opulent decision some are criticizing as hypocritical — while Shang-Chi star Simu Liu swaggered through in a Fendi white blazer with black accents. 

Singer Shawn Mendes took a more bold approach, pairing a leather, rock star chic look with his bare chest. 

Justin Bieber made a showing in a dark suit and suitcase from Drew House, the singer's fashion line. He arrived with his wife, Hailey Bieber, whose black column gown was a perfect match for Justin's outfit. 

Canadian tennis stars Felix Auger-Aliassime and Leylah Annie Fernandez arrived to the event slightly later.

But as athletes showing off their fashion prowess, they weren't alone. Gymnasts Nia Dennis and Simone Biles made an appearance — Dennis in a sleek blue bodysuit and Biles in a flowing gown. 

While Chance the Rapper, along with his partner Kirsten Coley, also appeared in co-ordinating black outfits. 

And Yara Shahidi wore silver custom Dior complete with a headpiece, saying she was inspired by performer and civil rights activist Josephine Baker. 

New Zealand pop star Lorde, who recently re-entered public life with the release of her album Solar Power, arrived with a crown.

Gigi Hadid revealed a Prada outfit paired with stunning red hair, while Jennifer Lopez's Ralph Lauren look had a distinct Old West inspiration. 

Frank Ocean's surreal fashion choice included an understated Prada jacket paired with a green robotic baby that moved seemingly on its own as he walked up the steps to the ceremony.

Anna Wintour arrived early, with a wave to the crowd, accompanied by her pregnant daughter, Bee, in a floral design with ruffles at the neck.

Considered fashion's biggest night, A-list guests from music, film, TV, tech and beyond are encouraged to embrace the theme of the new exhibition each year as they slowly make their way up the museum's red-carpeted stairs.

Interpretation is everything when it comes to how they dress — and how they enter.