RIHANNA PERFORMS @ THE HAMMERSTEIN BALLROOM!

She didn't call her new album Rated R for nothing. Rihanna performed a free concert in Manhattan at the Hammerstein Ballroom Thursday night in revealing outfit that didn't quite qualify as a dress.

The heavily embellished, metallic outfit plunged at the neckline and barely covered the Barbados-born singer's bum. But the style-savvy 21-year-old ensured certain lady parts wouldn't be making any unexpected appearances by wearing a matching silver bikini top underneath her outfit.

The collage-like minidress incorporated no fewer than 7 textures, including chain mail, knobby beads, and a skirt and sleeves consisting of layers upon layer of jagged points, for a Mad Max meets King Arthur meets Barbarella look.

Rihanna, who has been making the rounds in support of her new album, announced the last minute free show via her Twitter account. The first 800 people who lined up outside the Hammerstein Ballroom on the morning of December 3 scored tickets to the concert.

The space age apocalypse look was just one of the outfits she sported during the show. Singing her hit "Umbrella," she wore a silver leotard with small black wing-like shoulders and a strip of black around the waist that made her look like a modern pop superhero.

She strutted around the stage getting the crowd to sing whole verses of the song, before thanking MySpace and JetBlue for sponsoring the show.

The singer's ex, Chris Brown, appears on "20/20" to discuss his regrets over assaulting Rihanna after a pre-Grammys party last February.

The attack would appear to have been the farthest thing from her mind as she preened for the crowd Thursday.

This weekend Rihanna again perform in New York, on "Saturday Night Live."