The third annual iHeartRadio Music Festival is set for a September weekend in Las Vegas with performances by Justin Timberlake, Katy Perry, Tim McGraw, Queen + Adam Lambert, Bruno Mars, fun., Elton John, Keith Urban and many more. Commandeering the MGM Grand Garden Arena Sept. 20-21, Clear Channel’s yearly extravaganza of heavy-rotation artists will also … More iHeartRadio Music Festival Reveals Lineup