JUST ADDED: 5 Seconds of Summer will be rocking the stage at this year's iHeartRadio Music Festival Village in Las Vegas! The band sat down with Ryan Seacrest to break the news. Click here to buy your tickets now, before they sell out!
During a recent concert at the Adelaide Entertainment Centre in Australia this month, John Mayer channeled Beyonce when he covered her hit "XO."
He performed the cover acoustically with just a guitar and a harmonica ... and his lovely voice.
Check it out below!