Tolkien's Lord of the Rings trilogy is arguably the most metal book series ever written.
From Orcs to Mount Doom, from battle scenes to Mordor, the chapters of the book resonate well with metalheads, and so they should. Blind Guardian's Middle Earth infused lyrics or band names such as Gorgoroth, Amon Amarth, Cirith Ungol, Burzum or the entire discography of Tolkien-themed Battlelore mean that the impact of the little dwarfs and hobbits has been very significant on metaldom.
Peter Jackson's adaptation brought Middle Earth to life and to the minds of the illiterate. Even the musical score consists of many metal song intros and sound effects of battles and beasts.
When Jackson decided to resurrect The Hobbit, it was obvious that metalheads would flock to see the movie. One problem. While the movie is for metalheads, it has no metal actors. I'd like to think that this is not an omission, but simply a case of conflicting schedules. The movie is a long commitment, and it coincides with touring and recording sessions.
Here is a list of metal actors who were considered for the movie, but couldn't commit to the gruelling schedule: