New York, New York – Billie Eilish had some A-list fun at the Met Gala on Monday, and has shared new behind-the-scenes pics to prove it.

Billie was not channeling her typical grunge style when she attended fashion's biggest night on Monday.

She wowed on the red carpet in front of NYC's Metropolitan Museum of Art in a royal-inspired satin-corseted Gucci gown that was made from completely upcycled materials.

"I just wanted to be as eco-friendly as possible," Eilish told Vogue. She topped off her ensemble with a black choker and beige platform shoes made from vegan materials, too – in keeping with her Met Gala trend of pushing designers to be kind to animals.

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"A beautiful night," she wrote as she showed off her lewk on Insta.

But that wasn't the only part of the evening the 20-year-old showed off on the 'gram, as she revealed new photos on Thursday with some all-star pals.

In one epic candid bathroom mirror shot, she's flanked by models Hailey Bieber, Kendall Jenner, Winnie Harlow, YouTuber Emma Chamberlain, and actor Jenna Ortega.

In another blurry tongues-out photo, she poses with Lizzo and model sisters Bella and Gigi Hadid. Talk about some famous friends!

Another shot shows Billie smizing with Jared Leto and Dakota Johnson, followed-up by pics of what appears to be a sensible outfit change later in the night into a sleek black tux paired with a lacy tank.

Completing the Insta series with some shots in a crowded elevator and a boomerang in the back of a private car, it seems like Billie was Happier Than Ever in her sophomore Met Gala outing.