Can’t lie: I’ve had Sunday, August 31 circled on my metal-show calendar for months. Judas Priest, Motorhead, Heaven and Hell (aka Black Sabbath as fronted by Dio), and Testament rocking the same bill? It’s worth the drive down the peninsula to the Shoreline Amphitheater, where even sweaty mullets and overpriced fried grub won’t be enough to dampen the awesomeness of Metal Masters. It’s hard for me to type with both my hands curled into devil horns, but since Judas Priest guitarist KK Downing was kind enough to speak with me over the phone — from Belgium, no less — about Metal Masters, Priest’s new concept album, and the evergreen appeal of metal, I’ll do my best to transcribe our conversation here.