If that's not enough of a surprise, they've also revealed a brand new song with Chester on vocals called "Out of Time," which you can hear in the Soundcloud player below.
The surprise lineup was revealed at the annual KROQ Weenie Roast Concert in California at the weekend, which you can see in the YouTube player below.
They appeared after a set from Vampire Weekend, and began with a man on the drum riser with his back to the audience for the opening line of "Vasoline." Rolling Stone describes the moment he delivered the opening line to "Vasoline": "And with that, the venue exploded as Linkin Park frontman Chester Bennington turned and leaped into action ... Bennington did such an admirable job recreating Weiland's vocals on songs like 'Sex Type Thing' and 'Wicked Garden' that one listener backstage thought it had been the former STP frontman."
Chester admitted in a statement that he's a long-term fan of the band, so he's probably living out a teenage dream by fronting them right now. But he's also reassured Linkin Park fans that he won't leave Linkin Park for his teenage idols.
"I've loved STP since I was 13 years old and they've had a huge influence on me," explained Bennington. "When the opportunity came up to do something creative with them, I jumped at the chance. The guys in Linkin Park have been incredibly supportive of me undertaking this project while I've continued to work on new music with LP."
Watch Linkin Park frontman Chester Bennington in his debut performance with Stone Temple Pilots at the annual KROQ Weenie Roast here:
Listen to the brand new Stone Temple Pilots song "Out of Time" featuring Chester Bennington on vocals here: