Troy Van Leeuwen, Dean Fertita and Josh Homme of Queens of the Stone Age perform at Merriweather Post Pavilion. (Kyle Gustafson/for The Washington Post)

Electric guitars: What are they good for anymore? Can fresh ideas be wrung from their necks? Can we get them to cough up new secrets? Will they take us into the future, or just find new ways to send us back into the past?

Auspicious answers wafted through the air at Merriweather Post Pavilion on Thursday night where two very different acts — hard-rock vets Queens of the Stone Age and avant-pop phenom St. Vincent — each made a case for rock-and-roll’s six-stringed future.

This summer, after nearly 20 years spent releasing somewhat serviceable albums, Queens of the Stone Age is finally touring behind a terrific one, last year’s “ . . . Like Clockwork.”

The title might as well be a tribute to the band’s new drummer, Jon Theodore, who gave frontman and bandleader Josh Homme’s burly guitar riffs a refreshing swagger on Thursday night. (Theodore recorded just one song on “. . . Like Clockwork” — a majority of the album’s drum-bashing was handled by Dave Grohl.)

But on stage, Homme’s guitar consistently provided the quintet’s center of gravity, setting the mood, dictating the rhythm and steering the ship. He was the timekeeper and the showstopper during “Smooth Sailing,” a bruising, bouncing new song that threatened to eclipse the weapons-grade funkiness of Led Zeppelin.

Even better was “If I Had a Tail,” which felt as bright and alive as a downcast, mid-tempo rock song can feel. In the middle of it, Homme delivered a wonderfully ornery guitar solo, then resumed his sinister saunter.

Older hits — “Go With the Flow,” “No One Knows” — had the half-capacity crowd throwing clenched fists toward the July night sky, while the band’s new songs invited fans to put their hips into it — something Homme spent much of Thursday night trying to do himself.

But hips, schmips. Most fans were craning their necks for a glimpse of Homme’s fingertips as they did their dirty work, summoning ominous and splendid sounds.

When rock purists balk at electronic music, carping about the mysterious button-pushing that DJs and keyboardists do onstage, it’s partially because everything is laid bare with the electric guitar. The instrument is designed to showcase the mechanics of how it’s being played. It makes us feel as though we can’t be deceived.

But we can still be dazzled, which appeared to be the primary goal of St. Vincent’s opening set.

The singer-guitarist — born Annie Clark — took the stage before sundown wearing her silver hair in a Dutch crown braid and sporting an asymmetrical frock that evoked both “Game of Thrones” and senior prom, 1989.

This was going to be a show, and if her outfit didn’t make that clear, she opened her set with “Rattlesnake,” a song that peaked with a mesmerizing solo in which she dabbed the stings of her guitar with the fingers of her right and left hands, as if typing out a letter. As her heavy-metal guitar wizardry turned into alien babble, she gave the audience her best android gaze and allowed her lips to curve into the faintest smile.

The rest of the set felt looser and more magnetic than St. Vincent’s new self-titled album, which evokes the brainy quirk of her hero and sometimes-collaborator, David Byrne.

On Thursday, “Digital Witness,” the album’s other highlight, featured squirmy guitar phrases that felt particularly free, as if they were trying to escape the music and slip off into unmapped terrain.

It sounded a little like ’70s prog rock and even more like 21st-century progress.