More than 30 years together, Metallica remain among the most challenging rock bands on the planet. And while so many of their original contemporaries have either 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.