Billboard Music Awards host Chrissy Teigen

Billboard Music Awards host Chrissy Teigen photographed at Milk Studios in New York City on May 5, 2015.

Miller Mobley

Chrissy Teigen may be a world-famous supermodel who’s on a first-name basis with the president of the United States, but somehow the upcoming Billboard Music Awards host (and Billboard's latest cover star, along with co-host Ludacris) was still nervous to meet Justin Bieber. “It’s one thing to read about somebody all the time on the Internet and think you know about their lives,” Teigen tells Billboard. “It’s another thing to have to talk to them face-to-face.”

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Bieber will be a guest on an upcoming episode of Lip Sync Battle, the wildly successful Spike TV show that Teigen co-hosts with rapper-actor LL Cool J. “Someone told [Justin] that I was really nervous to be around him, so he did his best to make me not nervous, which made me extra-nervous,” Teigen explains. “It’s gonna be the most awkward thing on the planet, I think.”

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Bieber’s fake-singing exploits haven’t aired in full yet, but an online preview (above) shows the singer rocking out to Ozzy Osbourne’s “Crazy Train” while wearing a black hesher wig and making crazy eyes. “He’s just really fun,” Teigen reports. “The kid is so young still, but he does have this weird, charming way about him. I understand [now] why people found him fascinating about him in the first place. He’s a charming little bastard, and I fell for it completely,” she says, laughing. “I became a Belieber, for sure.”

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So far, Teigen’s mostly provided color commentary on the series but she too will perform her own fake-singing routine in the series finale -- a rendition that wasn’t entirely planned. “What I learned is that on Lip Sync Battle, the cameras are always rolling -- even during commercial breaks,” she says. So there were a number of occasions when she got caught up in the moment, performing songs for the room. “You think you’re doing it for just the audience, but no, you end up doing it for the world.”

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The song she ended up lip-syncing for the world? LL Cool J's graphic slow jam, “Doin’ It,” which she dueted on with her husband, John Legend. “I’m the worst dancer, there were no lyrics up and it’s obviously like the dirtiest song," she says. "Never in my life did I think I would sing 'Doin’ It' in front of LL Cool J, but now I have.”

Billboard Music Awards 2015