The 'Jennifer's Body' actress caused a stir on the red carpet at Brooklyn's Barclays Center thanks to her sheer illusion dress by Mugler, which showed off her silver underwear and she explained her boyfriend - who wore a custom crimson patterned tuxedo - had had a huge hand in deciding her look for the evening.
She joked to 'Entertainment Tonight': "He was like, 'You're gonna be naked tonight.' I was like, 'Whatever you say, daddy!' "
Megan admitted she was "so proud" of her boyfriend, who went on to win the Best Alternative award for 'My Ex's Best Friend' and performed 'Papercuts' with collaborator Travis Barker during the ceremony.
She added: "He's the most talented boy in the world."
And after appearing alongside the 31-year-old star in his 'Bloody Valentine' music video, Megan joked he won't be casting any other women in future clips.
She said: "He's not allowed to have other h**s in his music videos. It's the queen no one!"
Megan and Travis' girlfriend, Kourtney Kardashian, introduced the performance of 'Papercuts' to the audience, describing the singers as their "future baby daddies".
Megan shouted: "New York, I need you to get extra loud for our future baby daddies."
And Kourtney added: "Machine Gun Kelly and Travis Barker!"
Ahead of the ceremony, MGK and Conor McGregor were spotted squabbling on the red carpet.
A source told TMZ that Conor put his hand out to introduce himself to Kelly, but the star's team allegedly pushed him away.
Other footage showed the UFC star - who had some of his beverage spilled in the scuffle - later throwing what was left of his drink on the red carpet.
Conor later insisted "absolutely nothing" happened, and branded Kelly a "vanilla boy rapper".
He said: "I don’t know. He showed up, and I don’t know. I don’t know the guy.
"Nothing happened with me, I only fight real fighters, people that actually fight, you know what I mean?
"I certainly don’t fight little vanilla boy rappers.
"I don’t even know the guy. I don’t know anything about him, except that he’s with Megan Fox."
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