Alot of bands have covered Charles Manson songs. Alot of them not metal, but there close enough
Guns 'n Roses covered Manson's Look at Your Game Girl. It's a hidden track on the Spaghetti(spell?) Incident.
Marilyn Manson stole the words "I had a little monkey, I sent him to the country and I fed him gingerbread, Along came a choo-choo and knocked my monkey koo-koom, and now my monky's dead", for his song "My Monkey". Those wordes were first used in Charles Manson's "Mechanical Man".
M. Manson also did an acoustic verson of C. Manson's "Sick City"