Martin, who's introduced by KoL's Caleb Followill as 'the second most famous singer here today,' plays guitar and provides backing vocals as the band performs their song 'Fans'.
Kings of Leon was joined by a special guest when they headlined Radio One's One Big Weekend in Glasgow recently. The band brought out Coldplay's Chris Martin onstage during their set to perform a track together.
Before the performance, KoL's frontman Caleb Followill said of Martin, "We've got a little treat here. I'd like to welcome the second most famous singer here today to come join us on this song... He said he's not gonna sing but we'll see."
Gwyneth Paltrow's estranged husband then arrived onstage wearing a black jacket over a white shirt. He played his guitar and provided backing vocals as Followill tackled "Fans", a song from KoL's third album "Because of the Times".
"We finally have someone famous in our band," Followill joked after Martin exited the stage.
Kings of Leon is currently promoting their latest album, 2013's "Mechanical Bull". They are now gearing up for their U.S. tour which is slated to begin on July 31.
As for Martin, his band recently put out their new album "Ghost Stories". The LP landed at No. 1 on the U.K. chart earlier this week and is on course to make its debut at No. 1 on Billboard 200.