Black Sabbath's farewell concert, which included hits like "Iron Man" and "War Pigs," comes as the rocker is living with Parkinson's disease.

Bev Bevan explores the origins of heavy metal music and Black Sabbath's homecoming gig, with interviews and music from Black Sabbath, Judas Priest and Slipknot. As the music stops, fireworks go off above Villa Park as the founders of heavy metal bow out of their unbelievable career.