Simplify the following text for a Grade 4 native English-speaking person.
Original: The New Wave of British Heavy Metal ( frequently abbreviated as NWOBHM and pronounced ) was a heavy metal movement that started in the late 1970s , in Britain , and achieved international attention by the early 1980s .
Simplified: The New Wave of British Heavy Metal ( NWOBHM ) was a heavy metal movement that started in the late 1970s , in Britain . It was well known around the world by the early 1980s .