Metallica
Metallica, as Dehaan, perform a surprise set at the Orion Music Festival (Getty Images)

Dehaan, the mystery band on Metallica's Orion Music + More festival in Detroit, turned out to bear a more than passing resemblance to the festival's hosts on Saturday.

It was, in fact, Metallica, taking the Damage Inc. stage unannounced for a late-afternoon 30th anniversary performance of its 1983 debut album "Kill 'Em All."

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James Hetfield -- who shortly before the set sent out an Instagram photo of the stage saying "can't wait to see my Dehaan, my new favorite band -- came on stage first, asking the crowd "Does anyone know who they are? They're from Baltimore. Nobody knows anything about them but us" before being joined by his bandmates and charging into "Hit the Lights." Metallica roared through the 10-song set in nearly 55 minutes, stopping mostly to change instruments. 

Robert Trujillo deftly handed the late Cliff Burton's showpiece "Anesthesia (Pulling Teeth)," while fans -- many of whom were caught unawares and sprinted over from Orion's other four stages -- were clearly thrilled to hear less-played fare such as "Phantom Lord" and "Jump in the Fire," as well as favorite such as "Whiplash" and "Seek + Destroy."

Metallica stuck comically to the Dehaan identity throughout the set, finishing with Hetfield telling the crowd, "This is the last one for Dehaan. We appreciate your support and hope to see you again somewhere." After "Metal Militia," however, he said, "Thank you, Orion, for putting up with us and all our surprises. Next up…(1997's) 'Reload!"

Metallica is slated to close Orion on Sunday night. 

The group has been visible throughout Detroit during the days leading up to Orion. Hetfield and Trujillo attended a Detroit Tigers game on Wednesday night, and the band members appeared in Instagrams hiding free tickets around the Detroit metro area. All four members introduced Baroness on Friday at one of the official Orion pre-parties at Saint Andrews Hall. Throughout Orion's first day they appeared on stages to introduce bands, and Hetfield showed up at the car and motorcycle show he helps curate to press some flesh and pose for pictures with fans.