According to 'James Hetfield' Metallica: Some Kind of Monster (2004) was originally to be a 6 part mini-series for VH1 inspired by the success of MTV's The Osbournes (2002). However, after seeing much of the footage the band felt this was not a direction they wanted to take their careers and bought out VH1's rights to the material and made the film as you see it today.
In the DVD commentary (during the bassist auditioning scene), James Hetfield states that if Cliff Burton (Metallica's bassist early on in their career until his death in 1986) had auditioned for the band, they would not have picked him .
Due to the departure of full time bassist Jason Newsted, producer Bob Rock was asked to play bass on 'St. Anger'. Despite his acceptance of the temporary role Rock did not make any creative contributions to the album, and therefore didn't receive any writing credits.