Ah, to be young, cool and talented!

Lorde was already hip on record. The singer-songwriter, now 21, produced an acclaimed and adventurous album when she was 16 (David Bowie told a bandmate he thought Lorde was the future of music), and she followed that up with last year’s wonderful, Grammy-nominated “Melodrama.”

But her concert Saturday at Mohegan Sun showed that she’s just as cool live. Lorde’s voice was filled with experience, able to thrill with drama, delve into angst and hint at ennui. She might showcase a definite maturity in her songwriting and in her world-weary voice, but she exuded a youthful vibrancy onstage and a real joy in performing.

She tossed her bountiful head of brown hair as she jerked and swooned and flitted on the stage, as if possessed by her lyrics. At times, she could have passed for Florence Welch’s hippie-ish younger sister.

While all artists thank their fans, Lorde’s appreciation seemed more genuine than most. “Every day, I’m so grateful that you get it — you get what I’m doing,” she said, one of several moments of thanks. During her encore, Lorde (nee Ella Yelich O’Connor, from New Zealand) stepped down from the stage, stopping to hug fans and even kiss a couple of their hands.

The crowd, which was heavy on teen and 20-something females — when Lorde asked if there were a lot of college kids in the audience, the response was a roar — was downright adoring. (There were reports of Lorde not filling venues at some other stops on her tour, but not here; the Arena was packed.)

While Lorde’s sophomore CD “Melodrama” didn’t sell as well as debut “Pure Heroine,” you would have been hard pressed to realize that at the concert. Audience members responded just as enthusiastically to “Melodrama” numbers as to “Pure Heroine” chart toppers like “Royals” and “Tennis Court.” They pogoed like mad to “Green Light,” and “Super Cut” and “Perfect Places” were crowd ragers.

Lorde’s best vocals of the night, meanwhile, were on two slower songs. In “Writer in the Dark” (which she introduced by saying “We have to be the vivid dreamers … We have to be the hopeless romantics”), she finessed both the song’s deep dives and sky-high trills. And her voice flowed luxuriantly through “Liability,” where she was accompanied just by piano.

When it came to stage theatrics, Lorde was backed by a group of dancers who were dressed in casual off-white outfits that look as if they were heading for rehearsal rather than a performance. They executed modern-dance moves, but there was something disappointingly traditional about the choreography — something that didn’t jibe with Lorde’s forward-thinking music. It’s a shame the choreographers didn’t bring the gutsiness and edginess that, for instance, infused the dance on Sia’s most recent tour.

A huge glass box surfaced from below the stage, and the dancers would occasionally climb into it, staging little mini-dramas reflecting a song’s lyrics as the box was lifted on cables into the air.

Lorde used the box as a changing room at one point, which probably seemed better in concept than in execution. It slowed things down too much; there’s a reason there are usually quick-change people to help performers switch outfits rapidly backstage.

That said, Lorde’s trio of costumes were certainly appropriate for her — eccentric, eye-catching, but not too over-the-top. She segued from an orangey-red ensemble of MC Hammer pants and crop top; into a black outfit consisting of a sparkly black top that resembled a sports bra and a satiny skirt; and finally into a white top and diaphanous pants, with flamenco-like flounces.

In her between-song patter, Lorde displayed a disarming sense of humor about herself and about other matters; when a smoke machine became overactive, for instance, Lorde joked that she felt as if she were in a Shakespeare production. (And it wasn’t just Lorde; opening act Mitski almost disappeared in the voluminous smoke during her set.)

One thing I do wish: that Lorde had introduced or voiced appreciation for her band members, who were confined to the dark in the back of the stage all night. Give thanks to those who toil in darkness!