On a night when celebrities can let loose on their fashion choices, pop princesses and Hollywood actress took it up a notch in the avant-garde department at New York's Met Gala on Monday.

The 2017 Metropolitan Museum of Art's Costume Institute ball was themed 'Rei Kawakubo/Comme des Garçons: Art of the In-Between', an homage to highly structured creations of the Japanese designer and her avant-garde label.

Pop singer Katy Perry, a co-chair of the ball, lived up to the theme's challenge with a custom Maison Margiela 'Artisanal' ensemble by John Galliano, an imperial red tulle dress and a veil embroidered with the word 'Witness'.

Source: b'Katty Perry'
Source: b'Katty Perry'

Eric Wilson, fashion news director at InStyle, described this year's theme as "extremely challenging" compared to years past and agreed that Perry's outfit was courageously on point. "I think she's without a doubt the hit of the night so far," Wilson said. "It's very brave to wear something that disguises who you are so much on the red carpet."

Rihanna was no slouch either, embodying Kawakubo’s penchant for dramatic silhouettes in a custom Comme des Garçons floral dress with cutouts and oversized ruffles. The singer earned the most mentions on social media, said Kellan Terry, an analyst at the social media monitoring company Brandwatch.

Source: b'Rihanna\xc2\xa0'
Source: b'Rihanna\xc2\xa0'

Trench coat all the way.

Donning a beige Ralph Lauren trench coat gown paired with big silver hoop earrings, actress Priyanka Chopra dropped jaws and turned heads. 

Source: b'Priyanka Chopra\xc2\xa0'
Source: b'Priyanka Chopra with Nick Jonas\xc2\xa0'
Source: b'Priyanka Chopra\xc2\xa0'

Not to miss out was Deepika Padukone.

Here's a video marking her presence:

This is where it's at and yes, that is indeed Catherine Deneuve XPG.

A post shared by Prabal Gurung (@prabalgurung) on

'Happy' singer Pharrell Williams in jeans and leather jacket, and star couple Tom Brady and Gisele Bundchen in matching silver helped fashion maven and Vogue editor-in-chief Anna Wintour host the annual fundraising gala, which is sometimes referred to as "the Oscars of the East Coast."

Source: b'Tom Brady with Gisele Bundchen (L) &\xc2\xa0Pharrell Williams with\xc2\xa0Helen Lasichanh'

Reality TV star Kim Kardashian went against the theme, sporting a white dress by Vivienne Westwood with no clutch, no jewelry and no Kanye West, her fashion-loving husband.

Source: b'Kim Kardashian'

Kendall Jenner dared to be bare, wearing a sheer slip that left little to the imagination, both in front and back. 

Source: b'Kendall Jenner'

Tennis star Serena Williams also served up drama with a baby bump under her green Atelier Versace dress.

Source: b'\xc2\xa0Serena Williams'

Here's a look at other scores of celebrities who attended the gala:

Source: b'Selena Gomez with The Weekend'
Source: b'Hugh Jackman with Deborra-Lee-Furness & Matt Damon with Luciana Barroso\xc2\xa0'
Source: b'Blake Lively (L) and Kylie Jenner (R)'
Source: b'Miranda Kerr (L) & Katie Holmes (R)'
Source: b'Halle Berry (L) & Nicki Minaj (R)\xc2\xa0'
Source: b'Emily Ratajkowski (L) & Rose Byrne (R)'
Source: b'Bee Shaffer (L) & Sophie Turner (R)\xc2\xa0'

(All Image Source: APF, Reuters)