Simplify the following text for a Grade 8 native English-speaking person.
Original: The first wave began in the early 1980s by bands such as Venom , Bathory , Hellhammer , Celtic Frost and Mercyful Fate .
Simplified: This so-called `` first wave '' included bands such as Venom , Bathory , Hellhammer , Celtic Frost and SarcÃ fago .