"Behind the Metal Curtain" delves into the creation of "Metalocalypse: Army of the Doomstar" with interviews featuring show creator Brendon Small and his team of writers, animators, and musicians. They discuss the inspirations behind transforming the popular Adult Swim series into its first feature film. The documentary also includes special guests Kirk Hammett from Metallica and Andrew Kevin Walker, the writer of David Fincher's "Se7en" and "The Killer."