Taylor Swift accepts the award for top artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Brian Kelley, left, and Tyler Hubbard of Florida Georgia Line accept the award for top country artist at the Billboard Music Awards at the MGM Grand Garden Arena. (AP)
Taylor Swift accepts the award for top billboard 200 album for "1989" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Meghan Trainor accepts the award for top hot 100 song for "All About That Bass" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Calvin Harris poses in the press room with the award for top dance/electronic artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015. (AP)
Hozier poses in the press room with the awards for top rock artist and top rock song for "Take Me to Church" at the Billboard Music Awards at the MGM Grand Garden Arena. (AP)
Niall Horan, from left, Louis Tomlinson, Harry Styles, and Liam Payne of One Direction accept the award for top touring artist at the Billboard Music Awards. (AP)
Taylor Swift accepts the award for top female artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
John Legend accepts the award for top radio song for "All of Me" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Sam Smith is seen on screen accepting the award for top male artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Iggy Azalea, left, and Charli XCX accept the award for top rap song for "Fancy" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Taylor Swift accepts the award for top billboard 200 album for "1989" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 17, 2015, in Las Vegas. (AP)
Louis Tomlinson, from left, Niall Horan, Harry Styles, and Liam Payne of One Direction accept the award for top duo/group at the Billboard Music Awards. (AP)
Who's taking home the top prize at the 2015 Billboard Music Awards? Check out all the winners!