The party's just starting at the Billboard Music Awards.
Pitbull, Christina Aguilera, Macklemore and Ryan Lewis, Selena Gomez, the Band Perry and Kacey Musgraves have joined the star-packed performance lineup for the May 19 ceremony, which already includes Prince, Justin Bieber, Taylor Swift, Bruno Mars and Miguel. Bieber, Swift and Mars are also vying for the Milestone Award, presented by Chevrolet, which is a fan-driven honor that one voter will get to present at the show alongside Cee Lo Green.
Swift, fun. and Maroon 5 lead the finalists at this year's event, with each included in an impressive 11 categories. Rihanna competes in 10 categories, including Top Artist against Swift, Maroon 5, Justin Bieber and One Direction, while a pair of younger artists -- Carly Rae Jepsen and 1D themselves -- are finalists in nine and eight categories, respectively.