Ariana Grande and Miley Cyrus
Ariana Grande and Miley Cyrus sang a cover of "Don't Dream It's Over."
Pharrell Williams and Miley Cyrus
Pharrell Williams and Miley Cyrus performed "Happy."
Niall Horan performed "Slow Hands" and "This Town."
Robbie Williams and Take That
Take That briefly reunited with Robbie Williams onstage. However, the two performed separately, not together.
Little Mix performed.
Miley Cyrus and the Black Eyed Peas
Miley Cyrus and the Black Eyed Peas watched Ariana Grande perform.
Marcus Mumford opened up the show with "Timshel."
Justin Bieber fought back tears after performing two songs, "Love Yourself" and "Cold Water."
Ariana Grande opened up her set with "Be Alright."
Katy Perry danced around the stage while performing "Roar."
Ariana Grande and the Black Eyed Peas
Ariana Grande joined the Black Eyed Peas to perform "Where Is the Love."
Ariana Grande and a school choir
Ariana Grande performed "My Everything" with a school choir.
Miley Cyrus sang "Inspired."
This article originally appeared on PEOPLE.com.