Who let the folk in? Boston Calling kicked off the sixth installment of the biannual music festival Friday night, and there was more than a little kick (drum) to go around.

The night was anchored by headliners the Avett Brothers, who have more albums to date than the top two artists on the billing for Saturday and Sunday nights combined (Alt-J, Alabama Shakes, Chvrches and Hozier have seven albums to their names to Avett’s eight). Numbers aside, the Avett Brothers are nothing if not consistent.

The band’s sound is perfect for arenas and in the concrete monument of City Hall Plaza. Songs like “Kickdrum Heart” and “Head Full of Doubt / Road Full of Promise” filled the plaza with twangy instrumentation and vocals. The audience responded in kind with handclaps and footstomps.

The band encored with “Slight Figure of Speech” off I And Love And You, which devolved into a jam fest, but the Avett Brothers didn’t tear the place down so much as whet the appetites of festival-goers.

Iceland’s Of Monsters and Men, a festival alum and festival favorite, were in the middle of the evening’s 3-band itinerary, and went on as fall’s fading light drained out of a mostly clear Boston sky.

The band has an almost cinematic quality about it, with booming drums and horns. At points, especially the closer “Six Weeks,” you’d be surprised you weren’t listening to an Arcade Fire demo circa Funeral. When it was going for those grandiose, soaring gestures, Of Monsters and Men truly shined.

If there’s one artist who might be considered a gem or great find this weekend for many, it’s Gregory Alan Isakov. He had the tall task of playing not 15 minutes after the gates to the festival opened, when most are getting 21+ bracelets or finding their friends who got there before them.

The Colorado-based folk singer was a great late addition to the fest, replacing The Staves. Isakov performs in his own words “sad bastard” banjo music. That self-assessment is true, and while these tunes certainly might play well in a club or theater, Isakov and his band know how to tailor a setlist to the audience. The drums bursted forth, violin and guitars were loud, all while maintaining the emotional honesty present in Isakov’s work.

Since the expansion a three-day fest in 2014, the Friday night shows have always had the most cohesive feel to it. Earlier this year, Beck, Tame Impala and Sharon Van Etten were Fridays performers, which all had a very similar appeal. Saturday’s and Sunday’s are often more of a mixed bag – Sturgill Simpson, a folk singer, is mixed in with Chvrches on Saturday, for instance – whereas Friday feels like a concert.

In all, the first night of Boston Calling was a solid kickoff to the weekend ahead.

<p>Read a preview of Saturday’s performances.