The legendary frontman has revealed that he has recorded vocals for the band's 2013 release.
Plant previously played harmonica on 'The Lord is My Shotgun' for the 2002 album Evil Heart.
"I sang a bit on the Primals stuff because I think their references on looking back on the glorious past and the way they bring them into the contemporary world are fantastic," he told Mojo.
Plant said that he wanted to make music but was not interested in forming a new band or embarking on a new solo album.
"Everything we did back in those days and everything I have done since has been based on a fresh approach," he said. "What's going on? What can I be as a singer that doesn't play much?
"That's how I see everything: what can I be a part of that's exciting? And if anybody's got any ideas then I'm always up for it."
Listen to 'The Lord is My Shotgun' below: