This weekend metal fans were treated with an up-close and surprise appearance by Metallica at one of the smaller stages at the Detroit stop of the Orion Festival.

The Vans stage 4:30 slot was to feature an unknown band called Dehaan. But, as you'll see in the video below, James Hetfield sauntered on stage to 'intro' the "band", only to bring the rest of his boys out and launch into the full set of Kill 'Em All.

Some eagle-eyed metal heads saw this coming as soon as the banner for Dehaan was revealed, as the band name was 'spray-painted' with a huge X over it and the words 'Metal Up Your Ass' emblazoned above it. As many know, that is the ORIGINAL name for the 'Kill 'Em All' album. It was also the anniversary of the album's release.

At the first power riffs of 'Hit The Lights' roared over the crowd, hundreds came scrambling from all over the festival grounds to hear and see Metallica play a small stage.

Lucky bastards.

WATCH THE FIRST SET OF METALLICA'S SURPRISE SHOW AT ORION FEST