Being that it was Metallica's event, fans were definitely expecting to see the band play at the Orion Music + More Festival, but even with that knowledge the group was able to pull off a surprise. Late in the afternoon, frontman James Hetfield took the stage to introduce the band Dehaan, but then shocked everyone by remaining onstage as his Metallica bandmates arrived to unleash the group's 'Kill 'Em All' as word of mouth spread and fans raced toward the stage.

For those wondering about the name, it's a nod to actor Dane Dehaan, the star of the band's upcoming 'Metallica Through the Never' 3D film. As Hetfield arrived at the mic, there was a sparse crowd gathered and the frontman stated that all that was known of the mystery band was that they were from Baltimore.

Fan-filmed footage of the opening of the set (courtesy of WGRD) can be seen below. As previously stated, the group performed 'Kill 'Em All' in its entirety. The disc, released in 1983, will be celebrating its 30th anniversary next month. As expected, songs like 'Hit the Lights,' 'The Four Horsemen,' 'Jump in the Fire,' 'Whiplash' and 'Seek and Destroy' all received major applause from the crowd.

Check out the videos and the Dehaan setlist below:

Dehaan (aka Metallica) 2013 Orion Music + More Setlist:

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'