"He told friends three days ago that he got engaged," adds a source. "The ring is a black diamond set in white diamonds."
Patterson, 37, who is the former touring guitarist for Korn, popped the question over the weekend while he and Electra were in Las Vegas to celebrate her 36th birthday, says the source. The couple have been dating less than a year.
This will be the third marriage for the actress-model, who was previously wed to rocker Dave Navarro and, briefly, to NBA star Dennis Rodman.