"iHeartRadio Music Festival, Night 1"

This concert extravaganza, filmed over two nights at the MGM Grand Hotel in Las Vegas, features performances by some of the music industry's biggest names, including Katy Perry, Fun., Elton John, Keith Urban, J Cole, Queen + Adam Lambert, Muse, Tiesto and special guest Robin Thicke, among others.  Cast members from The CW's series will be on hand to help get the party started.