I love talkbass and have been using it for forever, but collectively, there is very little knowledge about metal on this website. A lot of people like to give their 2 cents but lack real knowledge about metal. Bloodhammer seems to have the right idea about it.
Simply put, metal isn't for everybody. Metal requires active listening. It takes time to fully appreciate the finer aspects of all the styles of metal. There are bands I hated initially, but have grown to love. Usually for similar reasons as stated above, its all screaming/growling, nonstop double bass, too harsh, bad production, etc... But the truth is that I did not really understand it when I first heard it. Frequently there is a message or feeling the song is communicating and the techniques used to achieve that sensation are taken to whatever level deemed necessary by the songwriter. That is the appeal of metal, there are no limits, no matter how minimal or technical, slow or fast, brutal or melodic. Just about everything is fair in metal.
Metal has many philosophical concepts that are brought to life through riffs, drums, and vocals. They can be anything. Nihilism, romanticism, nature, gnosticism, paganism, death, partying, political/social issues, women, drugs, religion, hate, elation, the universe, nationalism, literally anything.
Obviously there are terrible metal bands, but there are plenty of good ones who are capable of conveying overwhelmingly intense emotions. The capabilities of metal are infinite.
That said, I'm not some dingleberry without a sense of humor, and I listen to tons of different music and consider myself a musician above metalhead. Metal is theatrical and very aesthetic, and often times over the top, but thats whats awesome about it. Perfect example of this is King Diamond. Undeniably theatrical, over the top vocals, tongue in cheek attitude, yet absolutely ripping solos with arguably some of the best solo phrasing in metal and super catchy riffs.
If you've got any questions or want any band recommendations, no prob. My favorites are black, death, and doom metal but of course there are gems anywhere you look.
Horns up, \m/