Generally, heavy rock = heavy strings. Heavier (or thicker) gauge strings tend to give a fuller more bass-rich sound when played hard and also take the pounding of heavy strumming. The downside is that they're harder on the fingers, especially for beginners, and are more difficult to bent when playing lead. 11 gauge string sets are the most popular for pro Heavy Metal. (See here for discussion of what gauges mean!)  read more »