Stefani joins performance lineup.

The 15th annual Billboard Music Awards gala, set for Dec. 8 at the MGM Grand Garden Arena in Las Vegas, continues to take shape. TV and radio personality Ryan Seacrest will host the ceremony, reprising his role from last year's awards.

Gwen Stefani is confirmed to perform at the show, joining a lineup that also includes Usher, Nelly and Green Day.

Paris Hilton, Nicole Richie, Tara Reid, Big & Rich, Kelly Osbourne, Gretchen Wilson and Macy Gray will make appearances during the event, which is set to air live on the Fox network.

Additional presenters and performers, as well as finalists for the awards, will be announced in the coming weeks.