Swift's illness was only apparent between songs, speaking with the crowd. Otherwise, she was spot on through her vocals and brought a powerful energy to launch the show, performing "Blank Space," "I Knew You Were Trouble" and "Love Story."
"This is the best time I've ever had while having laryngitis I can tell you that," she said and later delivered a heartfelt thanks, noting her three Grammy nominations announced earlier Friday.
With her 25th birthday approaching next week she said this has been the best year of her life before asking, "Now would you like to dance?" And launched into "Shake It Off," inciting grooves across the thousands of seat rows, three levels and floor.
Few acts that followed could compare to Swift's star power, in some ways making her an odd choice to open the four-hour show rather than close it. But this decision also made sense: Rather than starting with a lesser known act like Becky G, who had the unfortunate slot following Swift, the top-charting mega star provided a massive infusion of energy early on that carried through the lineup.
The colorful Canadian newcomer Kiesza made a strong impression during her quick set with her single "Hideaway" performed with throwback pop and lock dance choreography that never compromised her singing. Pharrell delivered a medley of hits from his massive catalogue, including Snoop Dogg's "Drop It Like It's Hot," "Blurred Lines" and "Get Lucky," and introduced surprise guest Gwen Stefani as the "Queen of L.A." for their new song "Spark the Fire."
"No way in the world I could come to California, do a song with the most awesome girl in the world and not do it for you," he said.
Nick Jonas received one of the most piercing applauses of the night, as the crowd fawned over the grown-up Disney star's opening song "Chains," while he worked a bad-boy leather jacket and microphone stand crooning out over his backing track. The night's impressive surprise guests continued next with Demi Lovato, who joined Jonas for their song "Avalanche," enacting giddiness throughout with her amazing voice, before Jonas wrapped the set with "Jealous" accompanied by the gospel choir from a music video he released last month.
Sets by Charli XCX, Rixton, Shawn Mendes, Rita Ora and Meghan Trainor followed, showing off some of pop's biggest up and comers, as well as a quick surprise appearance by Ed Sheeran.
"I didn't know I was doing this until today, but this will be fun," Sheeran told the crowd and belted out "Thinking Out Loud" while strumming his guitar solo.
But it wasn't until Iggy Azalea took the stage that the excitement picked up severely again and carried out most the rest of the night.
The Australian rap phenom kicked her set off with a bad-ass swagger, welcoming her buddy Ora out for "Black Widow," pumping up the arena with backup dancers and a multi-leveled stage setup that blasted out an LED light show. Azalea continued her set with "Beg For It" and "Fancy," joined by Charli XCX wearing sneaker-style high heels. Comparatively, Azalea spoke very little, but instead let her hits do the talking, looking out triumphantly as the stage rotated around away from the crowd for the next act.
Jessie J followed with "Burnin' Up," noticeably without backup dancers as most the night's other artists had. She instead carried her quick performance solo with little more than basically a white swimsuit and sweatshirt on and an amazing vocal performance.
Ariana Grande was next and quickly challenged Jessie J and Lovato as the best female singer of the night. She opened with "Problem," noticeably without Azalea, and then welcoming The Weeknd onstage for "Love Me Harder." Dressed in a sparkling red two-piece outfit with white fluffy cuffs, she was the only act of the night to really look in the holiday spirit, probably in part to support her new Christmas single, "Santa Tell Me," which she introduced asking, "Are you all ready to hear some Christmas music?"
The crowd did not seem entirely ready, at least, as the track was a noticeable lull in the singer's set, performed with the sort of campy dance moves that conjure the season but little passion. "It's snowing in Los Angeles, who knew?" she said as some fake snow fell over the stage.
But the heat was turned up again quickly with "Right There," which she said is her favorite song off Yours Truly, joined by boyfriend Big Sean dressed in a matching red flannel shirt. As the song progressed, the two played off sexual tension making for a steamy performance until at the very end when Big Sean leaned in to kiss his beau and she turned her head away, rejecting him. The diss was soon forgotten largely as Grande reappeared with Jessie J for the two's hit "Bang Bang," pairing their incredible vocal talents, while Grande also rapped Nicki Minaj's part to her track.
In a lot of ways, Sam Smith, with his six Grammy nominations earlier that day, felt like the night's headliner, taking the stage dressed in all black and conjuring an emotional response throughout the venue with opening song "Nirvana."
"Last time I was in this room I was watching the Grammys, I was sitting in the way way back, and today I found out I was nominated for six Grammys," he said with a charming smile before announcing his guitarist Ben's birthday and starting into "I'm Not The Only One." He followed with Disclosure's "Latch," calling it the "song that changed my life."
Closing with "Stay With Me," he told the crowd, "Right now I need to see every single person in this room sing this as loud as they can." Though sing-alongs had been attempted a few times in the night, this by far was the most successful, creating a truly impactful communal concert experiences with the track's chorus radiating through the audience.
But Smith wasn't the closing act, 5 Seconds of Summer was. And as the singer closed his set, a noticeable age difference was suddenly drawn in the crowd, with about a quarter of the audience exiting immediately following. Meanwhile, the younger 5 Seconds of Summer fans were ecstatic at the pop punk quartet's arrival, making up for anyone who left prematurely with some of the night's loudest shrieks.
"Los Angeles you still awake?" drummer Ashton Irwin shouted out following the loud and raucous "Good Girls." With the time past midnight, they launched into "Voodoo Doll." But the Australians must have noticed the gradual emptying of the audience, because they kept making notes to the time and their perceived lack of excitement.
"Are we late? I'm glad my mom let me stay out this late," one said as they all introduced themselves by name before playing "End Up Here."
They continued to complain, with one saying, "It's a shame some people aren't screaming." Bassist Calum Hood then said, "I'm sorry for the people who don't like us." Lead singer Luke Hemmings followed, saying, "I'm sorry for the people who were asleep when we came onstage," presumably dissing Smith's set before and now about only half-full Staples Center.
Somewhere someone even dropped the F-bomb, as they mocked the ticking clock in front of them counting down their allotted set time and closed with "Amnesia," their cover of the Romantics' "What I Like About You" and "She Looks So Perfect" with synchronized jumps off their amplifiers along with pyrotechnics and confetti blasts into the air.