Pop goes the Jingle Ball: Ariana Grande, Jessie J and Iggy Azalea

Without a doubt, KDWB's annual Jingle Ball had its best lineup ever on Monday at Xcel Energy Center in St. Paul.

No, there wasn't a Miley Cyrus (like last year) or a Justin Bieber (way back in 2009). But this expanded lineup boasted four of the year's hottest pop names — Iggy Azalea, Ariana Grande, Jessie J and Meghan Trainor — who have been nominated for Grammys and reached the Top 5 of the pop charts. And a parade of other hitmakers.

Here are eight things we learned about today's pop music from the 12-act, 3½-hour Jingle Ball, which was seamlessly and stylishly produced by iHeart Radio.

Some of today's stars look and sound like the Top 40 audience. Becky G, 17, may have dressed in red fringe and sequins, but her voice and demeanor suggested Any Teen — with a screechy voice to match. Trainor, 20, may have looked like the girl next door, but her voice was more impressive in concert than on recordings.

Empowerment is a big theme with today's female pop stars. Trainor said it in her anti-Barbie body anthem "All About That Bass," Grande delivered the message in "Break Free," and OneRepublic served notice in "I Lived."

If you want to hook Top 40 radio listeners, add a little reggae. There is a reggae break in "All About That Bass," and Nico & Vinz use a reggae undercurrent in "Am I Wrong."

Last year's also-ran may be this year's star. Grande was positively underwhelming last year, looking like a lost little girl onstage, dressed up like a cutesy Christmas doll. This year, Grande, 21, owned the stage, romping around in stiletto heels and a black get-up inspired by a Playboy bunny outfit, and unleashing that big voice that has earned her the nickname of mini-Mariah.

Those Brit stars know how to command the stage. Even though they were given the shortest time onstage, Rita Ora and Jessie J made big splashes. With her Beyoncé-like vibe, Ora worked it, and Jessie J uncorked her magnificent soul siren on "Burnin' Up." Then Jessie produced the night's highlight when she belted "Bang Bang," note for note with Grande in one of the greatest vocal battles you'll ever hear in concert. That doesn't happen on regular tours — only on awards shows, TV programs and Jingle Ball tours.

Some newly minted stars are more palatable in smaller doses. While Aussie rapper Azalea seemed icy and detached in her 95-minute headline show in September at the University of Minnesota, she warmed up noticeably for her 25-minute Jingle Ball set. It didn't hurt that live-wire Ora perked her up on their duet of "Black Widow."

Cute guys will always get the loudest cheers in an arena full of tween and teen girls. Who received the most eardrum-shattering screams — host Nick Jonas or Shawn Mendes? It may have been a tossup, but the reception for Mendes, 16, an acoustic guitarist from Canada, was more vociferous for his arrival than after his songs. Oftentimes looks trump vocal skills in the pop world.

Sometimes you just wanna rock. That was left to Demi Lovato, 22, the Disney darling who channeled Pat Benatar for a moment, and mostly to OneRepublic, the old fogies and only band on the bill. Sporting a black-leather jacket, Ryan Tedder, 35, slew the 16,000 fans with "Love Runs Out," "Counting Stars" and a taste of Sam Smith's 2014 smash "Stay With Me," because Tedder, one of today's most successful producer/songwriters (he's worked with Beyoncé, Kelly Clarkson, Leona Lewis and others), knows that along with those empowering anthems, girls want romance, too.