As a huge Metallica fan myself I'd say the Black Album has more to its sound than it has to its songwriting, which is not a bad thing in itself but still a strong departure, even more so after an album like ...And Justice for All. I still really enjoy it though.

Soundgarden's career is a bit convoluted, but Badmotorfinger is my absolute favourite, the guitar sounds in there are absolutely gorgeous and the songwriting has something of this early 90s, hardboiled, Helmet-style grit that I've been digging, more particularly on songs like Slaves & Bulldozers or Mind Riot.

Also thank you for mentioning Fear Factory, this band never get enough credit and their first album is a classic