Filmmakers Joe Berlinger and Bruce Sinofsky have been shooting a Metallica documentary since last April and have revealed that the footage deals "with some really difficult subject matter," according

Filmmakers Joe Berlinger and Bruce Sinofsky have been shooting a Metallica documentary since last April and have revealed that the footage deals "with some really difficult subject matter," according to a post on Metallica's official Web site. "You don't wish bad news on anyone, but it unquestionably makes for drama and you're there to capture it," Sinofsky said. "So, the band going through some flux and some growing pains is the kind of material a filmmaker prays for."

Although bassist Jason Newsted had exited the group several months prior, the aftermath of his departure, along with frontman James Hetfield's battle with substance abuse, will likely make for compelling viewing. "Of course, on a personal level you don't want people to go through their tortures and dealing with their demons, but ultimately for the Metallica fan, they will see things they've never seen before," Sinofsky said. "And to quote Joe, 'I think right now we hit upon an amazingly important band going through some amazing changes.'"

Berlinger and Sinofsky first met Metallica when they obtained permission to use some of the group's songs for the documentary "Paradise Lost," a film about the West Memphis Three teenagers, who were convicted of a murder they insist they didn't commit.

The filmmakers say they have gained "unprecedented access to [band members'] private worlds," and "nothing has been off-limits." Sinofsky estimates that only 30-40% of the film has been shot so far, and that he is "hard-pressed to define the project because it's constantly changing."

No release date for the film, or for Metallica's next Elektra studio album, has yet been announced. Newsted's new band, EchoBrain, released its self-titled Chophouse/Surfdog debut today (March 5) in North America.