1. Thinking that metal was defined in the 80s and never should have moved past that point.
2. Taking itself too seriously.
3. "Rules" of metal.
4. Attempting to define what is or isn't "metal".
5. Insecurity (usually presenting as thinly veiled homophobia, machoism or sexism)
6. Douchebags in mosh pits that ignore the music and just want to hurt people or get hurt.
7. Douchebags on stage that encourage #6.
8. Bashing all other forms of music. (i.e. metal fans bashing punk music, forgetting that modern metal wouldn't be possible without thrash metal, which wouldn't have been possible without punk)
10. Image being more important than music (i.e. ignoring/bashing a band because of what they look like, or a band not putting enough effort into the music in favour of looking "trendy" and getting all their "moves" down)