Nu-Metal is trash...Think of any extremely popular mainstream metal band, like metal played on MTV instead of headbanger's ball. Usually that's nu-metal, and usually that's trash.
SOAD is hard rock, and I do like them, I think they are legitimate and talented, but I don't think they're metal. (That being said, I also don't think they're new metal)
For the record I like Mudvayne's LD 50, it isnt that bad of a record, even if it is a little soft. Any of thier new stuff is trash too.