Bruno Mars and his band kicked off the Billboard Music Awards in silky red suits that matched their silky dance moves, with bright gold disco balls hanging above them.
Mars performed his new single, the upbeat and old-school flavored Treasure.
Nicki Minaj, who is set to perform with Lil Wayne, won the first award for top rap artist, beating out Drake, Flo Rida, Pitbull and Psy.
"I definitely did not expect this one," she said, wearing a bright red dress.
Today's biggest stars - from Taylor Swift to fun. to Maroon 5 - are the key finalists at Sunday's awards show, airing live from MGM Grand Garden Arena in Las Vegas on ABC.
Those acts are up for 11 awards each; Rihanna, Carly Rae Jepsen and One Direction are up for 10, nine and eight trophies, respectively.
Most of the top stars will also blaze the stage, too, including Swift, Justin Bieber, Miguel, Macklemore & Ryan Lewis, Chris Brown, Selena Gomez and others.
Prince, who will receive the icon award, will also hit the stage, and Madonna, to be named top touring artist, will make an appearance.
Jepsen, whose nine nominations include top Hot 100 song for the ubiquitous Call Me Maybe, top female artist and top new artist, will also present an award.
"The Billboard Awards is kind of a nostalgic one for me because it was the first awards show I attended outside of Canada," the 27-year-old recalled in an interview. "I had never really done anything quite so big. And to be going back a year later, and to be nominated, and then to also being doing all the fun stuff like pick a dress, and see the party, and watch the show - I feel just lucky to be involved."
Jepsen's mentor, Bieber, is up for the night's biggest award, top artist. Other nominees include Swift, Rihanna, One Direction and Maroon 5. Swift is the only US act nominated for top Billboard 200 album for her multiplatinum Red, which will compete with One Direction's first and second albums - Up All Night and Take Me Home - Mumford & Sons' Babel and Adele's 10 million-selling 21, which won the award last year.
Bieber, Swift and Mars are also up for the fan-voted milestone award.
Comedian-actor Tracy Morgan the show's host. It's celebrating its third year back on the scene following a five-year break.
Jepsen, whose new single Tonight I'm Getting Over You features Minaj, said she's excited to see the rapper perform, but she's also happy to be in her seat and not onstage.
"I can remember being like just a big bundle of nerves last time," she said. "I've had a year of experience under my belt, and I'll probably still be nervous, but I'll be way more excited than anything."
Jennifer Lopez, The Band Perry, Pitbull, Christina Aguilera, Ed Sheeran, David Guetta and Kacey Musgraves will also perform Sunday night. Presenters include Shania Twain, Psy, Celine Dion, Miley Cyrus and CeeLo Green.