Rihanna, Britney Spears At Billboard Awards: Sing 'S&M,' Go Pantless

Rihanna may have taken a lot of hardware away from the stage on Sunday night, but it was what she didn't bring up in front of a national audience at the Billboard Awards that's making headlines.

Namely, pants.

Rihanna, who took three awards home on the night, rocked "S&M" in a spandex, pantless number, adorned with handcuffs and chains, just as her song describes -- hey, she says they excite her. Writhing around on stage, she gave the fans in the building and at home more than a thrill. And that was before a certain guest came on the stage.

Britney Spears, who teamed up Rihanna recently for a remix of the club hit, took the stage in a mask and black version of Rihanna's skimpy attire, and the two traded verses while making use of the conveniently arranged set.