Rock is possibly the largest genre of music you can find, it is a general genre with many sub-genres within it, from inspirational rock, soft rock, pop rock, pop, grunge, hard rock, metal. Then you get into metal witch is also rock, this particular sub-genre has it own sub-genres as in scream-o metal, black metal, death metal, love metal If you have heard of Nightwish you know there is even Opera metal.

Rock has been more translated to generalization of a part of the music industry that doesn’t have anything to do with other parts of the same genre like scream-o to pop.