The lineup for the sixth annual Scion Rock Fest has been unveiled. Among the 25 plus bands playing are headliners Machine Head and High on Fire along with Red Fang and Crowbar. The free event will be held at multiple venues in Pomona, Calif. on May 17.

And while it doesn't cost anything to attend, you must RSVP to secure your spot. You can do so beginning tomorrow (March 26) at 10AM PT at this location.

In addition to above mentioned acts, a ton of other bands playing many different styles of metal and hard rock will be part of Scion Rock Fest. You can check out Orchid, BL'AST!, Speedwolf, Power Trip, Jex Thoth, Coffins, King Buzzo, Big Business, Hot Lunch and Aqua Nebula Oscillator.

Also on the bill are All Them Witches, Pins of Light, Carousel, The Well, Midnight, Exhumed, In Cold Blood, Nekrogoblikon, Windhand, Lord Dying, Moab and Black Sheep Wall.

Machine Head have been hard at work on their next album. No release date has been announced, but the band will be releasing the new song 'Killers & Kings' as part of next month's Record Store Day. The 10-inch vinyl will have the demo of that song on the A side, backed with covers of Ignite's 'Our Darkest Days' and 'Bleeding.'