Originally Posted by ADD
None of those bands are very alike though
The closest link would be between Insomnium and Novembers Doom I guess. Swallow The Sun have some cool stoner rock elements which is what makes me give them the time of day in the first place, and Opeth is different than all 3 easily. Try looking at similar bands that come up when you do searches and things like that, their friends on Myspace, record label (biggest clue generally to finding more similar stuff), things like that will open up your avenues much more than any single band recommendation.
I feel that Insomnium, Swallow the Sun, Novembers Doom, and Opeth's harder stuff do sound similar......I found StS on Insomnium's myspace....so...I guess I will have to look harder