Metallica fans got a big surprise yesterday (June 8) at the Orion Music + More Festival when their heroes, who weren't supposed to appear until tonight, turned up for a surprise afternoon set and performed their entire 'Kill 'Em All' album.

The 4:30 spot at the Vans Damage Inc. stage was supposedly earmarked for an unknown band named Dehaan. However, based on this video, the fact that the band's logo was covered up and replaced with a hastily spray painted 'Metal Up Your Ass' message on the stage back drop seems to have given some fans a hint that a surprise was in store. ('Metal Up Your Ass' was the original title of 'Kill 'Em All.')

Sure enough, while James Hetfield was introducing "Dehaan," the true nature of the show was revealed when he instead grabbed a guitar as Lars Ulrich, Kirk Hammett and Robert Trujillo joined him on stage and launched into 'Hit the Lights,' the opening track from the classic (and soon to be 30-year-old) thrash masterpiece. If you're curious, Dehaan is the last name of Dean Dehaan, the actor who stars in Metallica’s upcoming 3D film ‘Through the Never.

As you can see in this amusing video, this surprise appearance sent fans scurrying to the stage, where the band played the rest of the 10-song album in order, including Trujillo's first-ever performance at late Metallica bassist Cliff Burton's solo piece '(Anesthesia) - Pulling Teeth.'

Watch "Deehan" Reveal Themselves as Metallica

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