Heavy metal giants Metallica played a set at the Global Citizen Festival in New York City's Central Park on Saturday night (Sept. 24), and they had a surprise up their sleeves: The band invited Mickey Guyton, who played the festival earlier that day, back to the stage for a performance of "Nothing Else Matters."

While it might seem like an unlikely onstage pairing, Guyton has history with the song: She covered it for the 2021 tribute album The Metallica Blacklist, a multi-disc project that also featured tributes from Darius Rucker, Chris Stapleton, Jon Pardi and Jason Isbell and the 400 Unit -- plus numerous other cover performances from stars hailing from a variety of genres.

After the set, Guyton expressed her Metallica fandom on her social channels. "There are no words. I'm just grateful," she wrote, posting a handful of snapshots from her time onstage rocking out with the legendary act.

During her own set at the festival, Guyton performed her new song, "Lay it On Me." Others who performed included Mariah Carey, Charlie Puth, the Jonas Brothers and more. The event will be televised on Sunday night (Sept. 25) on ABC, and you can watch Guyton's appearance in the video below, beginning around the :24 minute mark.

Ever since its launch in 2012, the Global Citizen Festival has been an annual event that calls on fans to take action against poverty in order to earn free tickets. Specifically, fans are allotted tickets after amassing a certain number of points through actions like calling representatives, signing petitions, participating in special challenges and more. Ways to take action -- including calling congress to fight deforestation, sharing a personal experience of the climate crisis and more -- are listed on Global Citizen's website.

Country Music's 30 Most Powerful Women Ever:

More From KUSJ-FM