Metallica pulled off the surprise of all surprises today (June 8) at their Orion Music + More Festival. During a slot that was scheduled for the mysterious band 'dehaan,' Metallica themselves appeared onstage and ripped through their 1983 debut album 'Kill 'Em All' in its entirety.

The metal goliaths were only scheduled to perform a headlining set tomorrow night (June 9) at the two-day festival at Detroit's Belle Island. However, fans got the thrill of a lifetime when Metallica played the Vans Damage Inc. stage today at 4:30 PM. It turns out that 'dehaan' is the last name of Dean Dehaan, the actor who stars in Metallica's upcoming 3D film 'Through the Never.'

Fan-filmed video of the opening of the set, during which frontman James Hetfield introduces 'dehaan' before the rest of Metallica appears onstage, can be seen below. With the 30th anniversary of 'Kill 'Em All' coming up next month, the band performed the album front to back during the blistering set. You can also check out footage (courtesy of WGRD in Grand Rapids, Mich.) of fans sprinting to the stage once they heard Metallica play the first few notes of 'Hit the Lights.'

James Hetfield Introduces 'Dehaan' (aka Metallica)

Metallica Surprise Orion Setlist on Saturday, June 8:

1. Hit The Lights
2. The Four Horsemen
3. Motorbreath
4. Jump In The Fire
5. (Anesthesia) Pulling Teeth
6. Whiplash
7. Phantom Lord
8. No Remorse
9. Seek And Destroy
10. Metal Militia