One Direction and Demi Lovato Perform at Teen Choice Awards

Video: One Direction and Demi Lovato Perform at Teen Choice Awards

One Direction opened the 2013 Teen Choice Awards, which was held at Los Angeles' Gibson Amphitheatre on Sunday night, August 11. The boys treated fans and other artists, who attended the event, with the first-ever live performance of their latest hit, "Best Song Ever".

Niall Horan, Zayn Malik, Harry Styles, Liam Payne, and Louis Tomlinson were seen packing the stage and greeting fans. They led the crowd to a massive sing-along and energetically danced to the fun song, which also serves as the soundtrack of their 3D concert movie "One Direction:This Is Us".

Also taking the stage was Demi Lovato. It was her first live performance after having her tonsils removed last month.

Donning a black jacket and black leggings, the 20-year-old singer rocked blonde hair which was styled in a half-up do. With perfectly applied eyeliner, mascara and eyeshadow, she looked totally like a rockstar.

The judge of "The X Factor (US)" performed "Made in the USA", the second single off her fourth self-titled studio album, "Demi". She teamed up with Nick Jonas, who played the drums in the background.

One Direction Performs "Best Song Ever":