Quote Originally Posted by The Man
Styles like death metal and doom metal are very far aside what you will hear on mainstream radio, but there is still significant difference between works of each style, and each style has its own history that is generally largely separate from the history of each other style. Just because you've never heard any music of a certain style doesn't mean that there aren't hundreds of bands that fit in each example. Power metal is not black metal is not sludge metal is not grindcore, and even though there are likely many bands that straddle the boundary between each set of styles, fans of one style are not always likely to appreciate the other styles, even if they seem relatively similar upon first listening. The only reason it all sounds the same on first listening is because you've barely ever heard anything like it before.
Exactly!

Although if someone claims that Power Metal and Grindcore sounds the same, he's most likely an idiot.