@xWKD Brilliant you just made my day.
About this topic, well.... I've seen some pretty weird things try and become a religion, for example The tube (the deity being a toilet roll tube decorated with pipe cleaners).
And then there's the weird religions that are.
Pastafarian - To worship the flying spaghetti monster.
The religion of the invisible pink unicorn.
Now there's this. My view is as follows. Why the hell not?
To talk about Buddhism though, you say that Gotamha Buddha is a supreme man. I negate your point. Buddha was just the first to reach enlightenment. People didn't follow him, they were already on the path before him. Therefore there is no idealistic way to show that the first Buddha is a supreme being. Shortly after him you have the laughing Buddha, he's no supreme being either. They were just people on the same path, on just reached the end first.
Heavy metal, if it wanted, could be a religion. I wouldn't follow it mind you, Scientology is my belief. However if someone worshipped metal as much as I know it can then metal can be a religion.