For those keeping track, this is the third time the most famous man in rap has graced an M.I.A. song, or sampled one anyway, rapping over “Paper Planes” on the posse cut “Swagger Like Us,” jumping on Arulpragasam’s “Boyz” back in an election year, and now blessing the artist’s clubby ode to frustrated love in the technological age, “XXXO.” There are more suitable songs on ///Y/ for a Jay-Z guest verse–“Story To Be Told,” say, or “Tell Me Why”–but we guarantee you’ll never hear a more vivid pronunciation of the word “metrosexual” in your entire life than the one Jay unleashes here. Still not satisfied with the amount of M.I.A. in your life? The BBC’s Zane Low premiered “Stepping Up” on the radio yesterday; it’s not on the official ///Y/ tracklisting people are working with, but it was on the version we heard, so we’re inclined to think it’s legit.