those bands dont even sound no where to each other, for the exceptions of hellyeah and mudvayne because they have the same singer. and some alternative metal can be considered metal if they have little outside influence, for example disturbed and godsmack. they dont sound like any other genre other than metal, maybe incorporating less than 15% of another genre. and as for hard rock, none of them are hard rock. hard rock is more like lordi, led zeppelin, ac/dc, ect.