LAS VEGAS — If you're wondering what tricks the Foo Fighters have up their collective sleeve for Sunday night's MTV Video Music Awards performance, let's just say you'd be foolish to miss it. (Check out photos of the Foo Fighters rehearsing for Sunday's VMAs with Serj Tankian.)

During the band's two-plus-hour rehearsal Saturday night (September 8) inside the Palms Casino Resort's Hot Pink Suite, the band jammed vigorously with a veritable who's who of rock and roll: Gnarls Barkley mastermind Cee-Lo, Queens of the Stone Age mainman (and avid poker player) Josh Homme, System of a Down's Serj Tankian and the one, the only, the legendary Motörhead frontman Lemmy Kilmister, who arrived sporting tight black pants, black boots, a black leather jacket and a scowl.

The Dave Grohl-led rockers will also invite QOTSA multi-instrumentalist Troy Van Leeuwen, the Eagles of Death Metal's Brian "Big Hands" O'Connor and Jesse "The Devil" Hughes (who, according to Homme, is the proud owner of "the world's greatest mustache, second only to Tom Selleck"), and Atlanta metallers Mastodon, who'll join the band for an epic rendition of Led Zeppelin's "Kashmir" (see "MTV VMA Race Is On: Justin Timberlake, Beyonce Lead Nominations").

Needless to say, the Foos set is going to be a tough one to top.

Tankian will also join the band Sunday night for a cover of the Dead Kennedys' "Holiday in Cambodia," while the gravelly throated Kilmister will handle lead vocals on two songs. That includes "Shake Your Blood" by Grohl side project Probot — Grohl will tackle drumming duties for that track, as he did on the studio version, which also featured Lemmy. They'll also perform a cover of Motörhead's "Overkill."

At one point during the relaxed and intimate rehearsal, Kilmister — whose four-string bass bears the words "Born to Lose, Out to Lunch" — taunted Foos guitarist Chris Shiflett for wearing earplugs. One couldn't help but feel like a fly on the wall in some basement where a group of old friends had gathered for a good-hearted jam session.

Grohl, who gnawed on the same piece of gum for the entire warm-up session, will stay behind the kit for a rendition of the Queens of the Stone Age's "I Wanna Make It Wit Chu." Grohl will of course be joined by Homme, Van Leeuwen, O'Connor and Cee-Lo, who is set to sing — but needs to learn the song's lyrics. The rapper had to refer to a lyrics sheet during the rehearsal but assured Homme he'd get them memorized before Sunday evening: "Don't worry, Joshua," Cee-Lo said with a wink and a smile.

Cee-Lo will inject some much-needed soul into one cover the Foos have become notorious for playing during their live shows: Prince's "Darling Nikki" (see "Foo Fighters 'Have No Idea' Why Prince Covered Their Song At Super Bowl"). After the boys ran through the song for the very first time, Cee-Lo — who had worked up a skull-covering sweat — and Grohl exchanged knowing grins. The cover was magic.

"That was sexy," Cee-Lo said to Grohl. And yes, it was certainly that.

(Cee-Lo's been a busy man in Vegas this weekend — in addition to jamming with the Foos, he's been meeting up with fans and trying his hand at poker.)

(Foo Fighters aren't the only ones who have been warming up for Sunday — check out Britney Spears rehearsing her big comeback, Kanye West testing out his intimate VMA suite and Nicole Scherzinger and Lil Wayne trying out their sexy preshow performance.)

Wait -- don't cash out on the VMAs just yet! From Britney's sultry comeback performance to the big winners, you saw it all -- well, almost everything! Get yourself even richer with our wall-to-wall show coverage, party reports, videos and loads more at www.VMA.MTV.com. For reports, photos, video and much, much more from previous VMAs, dive into the VMA archives.