Which SOAD album is your favourite?
If you're more into Toxicity / STA!, then you'll be better off looking at more metallic stuff. I recently got into Death By Stereo, a mixture of metallic elements and hardcore punk; you may also like some of the early work of Lostprophets (try the first two tracks from Thefakesoundofprogress) and ever tried Rage Against The Machine?
If you're more into Mezmerize/Hypnotize, then you'll be better off looking at the hard rock spectrum. The Darkness are a great band, although you may find the lead singer's falsettos irritating, in which case you may prefer the follow-up band Stone Gods - same guitarist, same style, different lead singer. And look also at stuff like Velvet Revolver.
