R.E.M. is best known as one of the forefathers of the alternative music genre, but in terms of sound I place them squarely in the folk rock tradition. Particularly on their early albums, you can trace Peter Buck’s guitar work straight back to The Byrds.
The band evolved into more of a rock sound — even grunge on 1994’s Monster and parts of subsequent albums — and also found success with the pop style (particularly on Green and Out of Time).