At the second installment of Metallica's Orion Music + More Festival, the legendary thrash band pulled off a massive surprise by performing their debut album, 'Kill 'Em All,' in its entirety. It was truly a once-in-a-lifetime experience, but for those who weren't lucky enough to see it for themselves, Metallica have posted some pro-shot video footage of the surprise set.

On Day One of Metallica's two-day Detroit festival, a mysterious band named dehaan was scheduled to perform at 4:30 on one of the festival's side stages. The banner for dehaan raised for the act's performance had their name crossed out with red spray paint, donning the classic Metallica phrase, "Metal Up Your Ass." After an introduction by frontman James Hetfield, the members of Metallica stormed the intimate stage and busted out 'Kill 'Em All' for the lucky fans in attendance.

The new video footage shows Metallica reheasing before the festival blitzkrieg. After the jam session, which features some awesome Kirk Hammett shredding, the video shows the band playing 'Hit the Lights' and 'Phantom Lord' from the Orion gig. Even more incredible, Rob Trujillo is wearing pants instead of shorts!

Check out Metallica's pro-shot footage of their surprise 'Kill 'Em All' show in the video above!