Think of "S&M" as part two of Rihanna's "good girl gone bad" phase-when the shock value of phase one starts to wear out, it's time to raise the stakes. So on the third single and opening track from her excellent "Loud" album, Rihanna embraces deviancy of the more eccentric sort-"sticks and stones may break my bones, but chains and whips excite me," she purrs on the chorus. Co-writer Ester Dean specializes in provocative pop, and Rihanna's voice offers the ideal vessel for some of her naughtiest lyrics yet. (See "Rude Boy," the pair's last hit collaboration.) With Stargate and Sandy Vee at the helm as producers, a skittering breakbeat leads into a monstrous bassline that thumps along with the singer's prodding. Radio might balk at the song's racy subject matter, but as far as the club is concerned, this is 100% pleasure.