The original Glam was a poppy UK (and NYC) pre-punk style that was often rhythm heavy, albeit with short snappy, almost Rock & Roll, songs. The artists wore heavy makeup and often outrageous costumes. It heavily influenced the second style below, and the UK punk revolution of 1976.
Poppy heavy metal music popular throughout the later 1980's and the first part of the 1990's. Vocals are usually harmonized and the songs are very accessible by mass audiences.