I think the Comic Strip presents series really nailed the silliness of metal lyrics with the Bad News episode. They went on to do an audio album which I had a copy of back in the day and the lyrics were hilarious - and funnily enouh, I've heard similar used genuinely on many occasions since.
I can still remember some pearlers like:
"Eat my brain - go insane"
"Ride the rat, night mare man"
"I'm a warrior the blood won't wash away
I'm a warrior, I'll kill myself one day!"