Brynjar Leifsson, guitarist for Of Monsters and Men, plays "Numb Bears" at the House of Blues Boston on April 7th. The Icelandic band released the US version of their debut album "My Head Is An Animal" in April 2012.

“Oh, wow. There are a lot of people here.”

On a stage covered in white Christmas lights, Nanna Hilmarsdóttir, female vocalist and one sixth of Of Monsters and Men, seemed genuinely surprised at the turnout. The band’s show at the Boston House of Blues had been moved there from the Brighton Music Hall, which had sold out. The group sold out the House of Blues as well.

Her surprise is warranted. A year ago, the Icelandic band was scarcely known outside of its home country; now the group is selling out venues all over the United States and Canada. Expectations ran high for the group’s first North American tour: its challenge was to wrest the explosive energy of their debut album “My Head Is an Animal” into an exciting live show. On Saturday, Apr. 7, OMAM left nothing to be desired. Its live show was a resounding affirmation of the promises of their charming and powerful debut album.

The group’s sound is at once familiar and refreshing. Most tracks start off with simple guitar strumming and hushed vocals before swelling and blossoming into catchy, exhilarating sing-alongs, complete with whole-band “la-la-la” choruses and shouts of “Hey!” that sound more like animalistic barks than indie-rock placeholders. The band’s unique brand of folk has drawn deserved comparisons to Arcade Fire, Edward Sharpe and the Magnetic Zeros, and Mumford & Sons. The band’s fantastical, often melancholy lyrics and foot-stomping arrangements have catapulted it to worldwide success in a very short amount of time.

The group found domestic success in 2010 by winning Músíktilraunir, an Icelandic music competition. It first started turning foreign heads in August 2011, when American radio stations began playing its debut single, the horn-driven romp “Little Talks.” As the group gained momentum abroad, things began to move fast; OMAM were signed to Universal and released an EP in December 2011. On Apr. 3 of this year, they released their full-length LP, “My Head Is an Animal,” in the United States. Since then, it has sold over 55,000 copies, reaching number 6 on the Billboard 200.

It was in the middle of this dizzying ride that OMAM walked onto the stage to a full house at the House of Blues. The band set up linearly across the stage, so that it was possible to see what every band member was doing all the time. During the few slow songs that involved only one or two people, the rest of the band looked unsure of what to do with themselves. But the setup’s purpose was clear during the louder songs, which made up the bulk of the set list. OMAM’s sizeable six-person roster—plus a seventh touring keyboardist/trumpeter—filled up the front of the stage. On songs like “King and Lionheart” and the unreleased closer “Beneath my Bed,” the entire ensemble was rocking out, and the group’s energy was more than infectious. The band had the entire audience cheering, jumping, and clapping along.

When the band started playing “Little Talks,” the audience went wild, matching each “Hey!” from the band and dancing energetically. This song seemed to be the main draw for most of the audience, and for good reason—the rest of the songs they performed had been released only four days before the concert. Those songs were still being digested; “Little Talks,” with its double-time kick drum and elegant male-female vocal exchange, felt like a classic in comparison.

OMAM’s success has been driven not only by its energy but also by its thoughtfullness and emotional depth. This depth manifested itself in the delicate exchanges between Hilmarsdóttir and male vocalist Ragnar Þórhallson. In several songs, like “Little Talks,” Hilmarsdóttir voiced anxieties and Þórhallson relieved them. In most, Þórhallson’s forceful tenor simply provided a textural counterpoint to Hilmarsdóttir’s atmospheric croon.

Throughout the concert, OMAM never once seemed disconnected from the people responsible for its success. Hilmarsdóttir said “Thank you so much!” after what seemed like every song. During “Sloom,” drummer Arnar Hilmarsson left his perch behind the kit and got the audience clapping along. And before “Lakehouse,” guitarist Brynjar Leifsson threw a custom-knit monster hand into the crowd—with the stipulation that whoever caught it had to give it to the person next to them.

“We are far from home / But we’re so happy,” Of Monsters and Men sang on second number “From Finner.” The band members were indeed quite far from home, but they never once seemed out of their element—and their happiness was contagious.

—Staff writer Matthew Watson can be reached at matthewwatson@college.harvard.edu.