The end of the world as we know it, and they feel fine. Sugarland covered R.E.M. at Merriweather on Sunday. (All photos by Kyle Gustafson/FTWP)

“We’re sure everybody heard it was supposed to be the Rapture. Well, we’re all still we thought maybe we should have a gigantic party,” lead singer Jennifer Nettles announced before the concert’s final song to the thousands crammed into Merriweather Post Pavillion. Suddenly, opening acts Little Big Town and Matt Nathanson appeared on stage for a rousing rendition of REM’s “It’s the End of the World (As We Know It),” complete with tambourines.

In the middle of the earnest “Everyday America,” Nettles broke into a medley of “Forget You,” “…Baby One More Time,” “9 to 5” and of course, “Bootylicious.” Who knew? The Cee-Lo/Britney Spears/Dolly Parton/Destiny’s Child combo is surprisingly catchy, perhaps for its randomness more than anything else.

The duo, comprised of Nettles and guitarist/singer Kristian Bush, drew headlines and criticism when they described their latest album, “The Incredible Machine” as influenced by steampunk, a sci-fi genre that ties together modern ideas with Victorian era-technology. The album strayed from the group’s country roots, with a mix of rap and rock and pop, plus a touch of reggae-rap in the up-tempo “Stuck Like Glue.”

An odd combination of songs on an album, though while performing live, the duo embraced its inherent weirdness to liven up the concert. Nettles appeared wearing an enormous mechanical-looking hoop skirt and twirled around stage while singing the slowed-down “The Incredible Machine.” And when Bush reprised the song later in the night, Nettles solemnly spray painted the word “LOVE” on a banner, and handed it to a member of the audience.

The always high-energy Nettles has the onstage persona of that quirky friend who can make the most mundane story seem like a must-listen. During “It Happens,” an ode to brushing off the little things that go wrong in life, Nettles used wildly expressive hand gestures and comically exaggerated facial expressions to describe such instances, from rushing to work without coffee to doing the walk of shame wearing two different shoes.

She used the same tactics during the opening lines of girl power anthem “Settlin’,” describing a lame first date: “Don’t know why I even try when I know how it ends/Looking like another ‘maybe we could be friends,’” she sang, throwing in some air quotes.

While Sugarland’s attempts to mix it up aren’t for everyone, the show on Sunday night brought out the quirkiness, right down the final minute – which is an idea that the duo itself embraces.