There are a helluva lot of reasons to cast aspersions on Mumford & Sons.

The British quartet is, after all, co-opting one of the last bastions of American music: folk rock. Yes, our neighbors across the pond have already asserted their dominance in the fields of R&B and soul (Adele) and jazz (Jamie Cullum), and now they’re going after the genre pioneered by the Byrds and Dylan. Ugh.

But when you watch these lads perform their infectious brand of galvanic, singalong anthems live, most—if not all—of these prejudices go straight out the window.

Mumford & Sons’ latest conquest was the Barclays Center in Brooklyn. The 18,000-capacity sports arena—home to the NBA’s Brooklyn Nets—was christened back in September with a series of Jay-Z concerts and will next play host to another Mumford show Feb. 12, followed by stints from Lady Gaga, Beyoncé, and Rihanna. Yes, these fellas are in that league.

In a scant one and a half years, Mumford & Sons has risen to become one of the biggest bands around. Their debut album, 2009’s Sigh No More, sold 626,000 copies in ’10 and then nearly doubled sales the following year, selling 1,282,000 copies—a rarity in music. Their sophomore LP, Babel, has sold over 1.5 million copies stateside since being released in September, and its opening-week sales of 600,000 were the most by any act in 2012 not named Taylor Swift. The group has also been nominated for six Grammy Awards, including Album of the Year.

To watch Marcus Mumford, the ringleader of the band, perform live is a sight to behold. In addition to his near-flawless vocals and jangling guitar, the singer also provides percussions on more than half their songs by furiously kicking a bass drum. He sings, plays guitar, and plays the drum all at the same damn time. It’s these three things, along with Winston Marshall’s banjo shredding, that allow Mumford’s anthems to truly take flight. And, when he’s not pulling off this impressive troika, Mumford assumes his post behind a traditional drum set, furiously pounding away while belting out lyrics, as on “Lover of the Light.” There is no denying it: this fella deserves to wake up to Carey Mulligan every morning.

And since I saw them last, at Coachella in 2011, the band has drastically improved on an already rousing live set. On this night, the four band members are flanked by a three-piece string section and three-piece horn section, transforming the twee-dressed foursome into a formidable, 10-strong collective. There’s some serious musical muscle behind their power ballads “I Will Wait,” “Little Lion Man,” and the aforementioned “Lover of the Light.” The tunes were also augmented by a stellar lighting setup, including flashing floodlights onstage, twinkling bulbs behind, and a makeshift canopy of Christmas tree lights hanging from the ceiling, bathing both the performers and onlookers in iridescence.

A few songs into the set, Mumford took to the mike, saying, “We were in Boston last night ...” The announcement was met with a loud chorus of boos (owing to the cities’ sports rivalries, naturally). Later on, the singer took a not-so-subtle jab at New York concert audiences’ reputation for reticence, saying that concertgoers usually “have their arms folded like, impress me; I’m from New York,” before proclaiming, “You have not been that way tonight!”

OK, they could use a little work in the banter department.

After performing a robust one-and-a-half-hour main stage set, the group shifted to a tiny square stage on the opposite side of the arena for a stripped-down four-song encore, culminating with “The Cave.”

While the “neu folk” movement has birthed a horde of bromidic acts, like the Lumineers and American Idol winner Phillip Phillips, Mumford & Sons manage to transcend their more pandering contemporaries through the sheer zest of their performances. This is spirited, catchy stuff that’ll have even its harshest detractors toe tappin’ along.