If you're going to pull off a shocking moment, Las Vegas is certainly the place to do it.

This weekend, an eclectic assortment of artists did just that at the iHeartRadio Music Festival, which touched down at T-Mobile Arena for two nights of epic performances. From Miley's classic rock covers to Green Day's political jab, we've rounded up 11 of the festival's biggest and boldest surprises. Check it out:

Lil Nas X joined the rodeo

He wasn't billed on the lineup, so you can imagine the hysteria that took over when Lil Nas X suddenly galloped in to perform "Panini" (sans choreo, sadly). He bounded offstage just as quickly, but returned after Camila Cabello's set for an encore of "Rodeo" and, of course, the little cowboy song that could, "Old Town Road."

Alicia Keys and Lewis Capaldi made everyone cry

Keys's hit-packed set — which included "No One," "Empire State of Mind," and "Girl On Fire" — reached its emotional peak when she welcomed Capaldi to the stage. The British singer-songwriter recently scored a smash with "Someone You Loved," and he and Keys beautifully belted the ballad together. The surprises didn't stop there — Keys also snuck a bit of Post Malone's "Congratulations" into the live debut of her new song "Show Me Love." Is there anything she can't do?

Miley Cyrus confused all the dads with her vintage covers

MC's first post-divorce concert was a crowd-pleasing spectacle. As we already noted, she rocked out to the live debut of her Ariana Grande and Lana Del Rey collab, "Don't Call Me Angel," before tearing through some of her most beloved solo hits. But it was her cover songs that truly shook things up — Miley busted out Led Zeppelin's "Black Dog" and Pink Floyd's "Comfortably Numb," quipping to the audience, "My favorite faces to see out in the crowd are confused dads."

T-Pain won the night

Lil Nas X manned the requisite "special guest" slot on Friday, but Saturday boasted an equally hype surprise: T-Pain, who got the crowd going with truncated versions of his biggest hits. And, in case you forgot, the man has hits aplenty — he flew through "Good Life," All I Do Is Win," "Got Money," "Buy U A Drank," and more.

Halsey opened with a song only true fans appreciated

Halsey's got a lot to look forward to, with her third album, Manic, on the way. But for her iHeartRadio set on Friday, she opted to dig into the archives, opening her performance with the 2015 Badlands cut "Gasoline." It wasn't all throwbacks, though — Halsey also took the opportunity to perform new single "Graveyard" for the very first time.

Backstreet Boys revamped their classics

Backstreet's back, but they're not quite the same. The beloved boy band (man band?) returned to Vegas for a set that dusted off some of their most iconic hits — with a twist. "Everybody" got a dubstep makeover, "I Want It That Way" got bolstered with a second-verse breakdown, and even the already-lit "Larger Than Life" boasted a fresher and louder arrangement.

Cage the Elephant stripped down and went upside down

You never really know what you're getting when you see Cage live, and that definitely rang true during the band's performance on Friday. Frontman Matt Shultz was a wild man with no plan — except to shed layers upon layers upon layers (seriously, how many layers?!) of clothes throughout the set. Barefoot and sweaty, he did a handstand at the front of the stage, then stripped all the way down to a sleeveless nude bodysuit while strolling through the crowd. His trek ended on top of a railing near the production booth, where he sweetly thanked fans for their love and for being present. (As if we had any choice other than being totally mesmerized by this man.)

Camila Cabello made "Señorita" sexy all on her own

Along with dancing through the live debuts of new singles "Shameless" and "Liar," Camila also treated fans to a solo rendition of "Señorita." And though we were all slightly bummed when she clarified early on that "Shawn's not here," it turns out the song's sultriness still holds up even when we don't have their onstage PDA to distract us.

Chance the Rapper was equal parts hype man and minister

Chano truly had something for everyone. He turned all the way up for "No Problem," then welcomed a squad of dancers for an exuberant rendition of "Hot Shower." But the rest of his set leaned toward the spiritual and introspective, with Chance doing his best Ben Gibbard impression on "Do You Remember," then bringing the praise for both the original and reprise versions of "Blessings." Good God!

Green Day took aim at Trump with a choice lyric change

The veteran rockers kicked off night one with a rousing rendition of "American Idiot" — on that album's 15th anniversary, no less. To give the 2004 anthem a modern twist, they changed the lyric "I'm not a part of a redneck agenda" to "I'm not a part of a MAGA agenda," brilliantly calling out Trump's "Make America Great Again" motto. Zing!

Monsta X's moves hypnotized everyone during their cameo in Steve Aoki's set

LOL, JK, this is no surprise at all. Just an excuse to watch these mega-talented boys in action!