Justin Timberlake accepts the award for song of the year for "Can't Stop The Feeling!" at the iHeartRadio Music Awards at the Forum on Sunday, March 5, 2017, in Inglewood, Calif. (Photo by Chris Pizzello/Invision/AP)
Drew Taggart, left, and Alex Pall, of the Chainsmokers, pose with the awards for best new artist, best new pop artist and dance song of the year for 'Closer' in the press room at the iHeartRadio Music Awards at the Forum on Sunday, March 5, 2017, in Inglewood, Calif.
Chris Martin, of Coldplay, third from right, winner of the award for best tour, and presenter John Legend, left, react as child performers read an acceptance speech on behalf of Coldplay at the iHeartRadio Music Awards at the Forum on Sunday, March 5, 2017, in Inglewood, Calif.
Members of Fifth Harmony from left, Dinah Jane, Lauren Jauregui, Ally Brooke, and Normani Kordei pose in the press room with their award for best fan army at the iHeartRadio Music Awards at the Forum on Sunday, March 5, 2017, in Inglewood, Calif.
Alex Pall, from left, and Drew Taggart, right, of the Chainsmokers, and Halsey accept the award for dance song of the year for 'Closer' at the iHeartRadio Music Awards at the Forum on Sunday, March 5, 2017, in Inglewood, Calif.
Timberlake won the night's first award, song of the year, for "Can't Stop The Feeling!" — his massive No.1 hit that was nominated for an Academy Award last month.
"I wrote this song because I wanted it to be about inclusion, about being together. And so I guess I want to take this opportunity and speak to young people right now 'cause there's a lot of you looking at me, if you are black or you are brown or you are gay or you're a lesbian or you are trans, or maybe you're just a sissy singing boy from Tennessee, anyone that is treating you unkindly, it's only because they are afraid or have been taught to be afraid of how important you are," Timberlake, who is from Memphis, said to the crowd at the Forum in Inglewood, California.
"Because being different means you make the difference," added Timberlake, who ended his speech with an expletive that was bleeped.
"Can't Stop This Feeling!" appeared on the "Trolls" soundtrack and was nominated for the best original song Oscar.
Mars, who earned the Innovator Award and closed the show, started his performance with his past hit, "Treasure," and later sang his newest hit, the groovy "That's What I Like." It featured his signature, slick dance moves and all-star band.
"Innovator is a very heavy word. ...It's a little ironic for me because I genuinely feel like I'm just getting started," Mars, 31, said onstage, sporting a black suit and sunglasses. "So buckle up. I don't know where we're going yet but we're going. Keep up y'all."
Other A-list stars were part of the awards show, too: Ed Sheeran started solo and strummed his guitar during "Shape of You" — currently No.1 on the Billboard Hot 100 — and later walked to another stage to perform "Castle on the Hill" with a full band. Sheeran won best lyrics for co-writing Justin Bieber's "Love Yourself."
"We started this song on the back of a tour bus," Sheeran said onstage next to co-writer Benny Blanco (Bieber, who didn't attend, also co-wrote the song).
Drake, who didn't attend the show, was the night's big winner with seven awards (he was also the top contender with 12 nominations). The Chainsmokers had 11 nominations and won five awards, including best new artist. The Grammy-winning EDM duo performed "Paris" and "Something Just Like This" with Chris Martin, who ran into the crowd during the performance.
"It's been a really, really tough year, but I hope that somehow this song made the summer a little bit better for you guys despite everything that's been going on," Halsey said onstage after she and the Chainsmokers won dance song of the year for their ubiquitous hit, "Closer."
Martin and his band Coldplay won best tour. He accepted the award onstage with three people — not his band mates — but child background dancers who performed with Katy Perry at the top of the show.
"Hello, we are Coldplay. Thank you so much for this award. We love our job and we love our fans," the young girl read from a paper. "You wouldn't believe it, but we are in our late 30s."
Perry, in a bright red blazer, hot pink pants and a short blond haircut, kicked off the show with kid dancers dressed as laborers when she sang "Chained to the Rhythm." Miley Cyrus was ecstatic as she introduced her younger sister, Noah Cyrus, to the stage for a performance. Miley and her parents sang along as Noah performed "Make Me (Cry)" alongside English singer-producer Labrinth.
Pop singer Shawn Mendes, rapper Big Sean and Thomas Rhett — who won country artist of the year — also performed at the show, attended by John Legend, Demi Lovato, DJ Khaled, Ansel Elgort, Macklemore, Jhene Aiko, Joe Jonas and more.
Some of the winners were announced on Snapchat, including Rihanna (R&B album of the year), Green Day (rock song of the year) and twenty one pilots (alternative rock artist of the year). Fifth Harmony, whose band member Camila Cabello recently left the group, won best fan army and thanked their feverish fans onstage.
Ryan Seacrest hosted the two-hour show, which aired live on TBS, TNT and truTV.