More than 30 years together, Metallica remain amongst the most challenging rock bands on the planet. And while so many of their original contemporaries have either "gone soft", run out of ideas or simply called it a day, the mighty Metallica continue to change, mutate and generally advance the metal genre in a manner no other group today has the capacity to equal. This documentary film traces the history of the band from their earliest incarnation as one of the "Big Four" of Thrash Metal, through the tragic death of Cliff Burton in the mid-1980s to the megastardom they enjoy today. And with the aid of exclusive and archive interviews, rare footage and location material, seldom seen photographs, commentary from the finest metal writers and a host of other features, it gets to the heart of what made this extraordinary group the primal force they have become.