The singing is usually the only thing that will put me off of a metal band. I can take some of the screaming, but if it's an album of continuous screaming, it becomes a bit much. I also don't like the opposite, which is the new fad of whining that is in some of the hipster metal.

The guitarist is the second thing to put me off. If there are no changes to speed and attack, and it's just 100 mph for every song, that's a bit much. I like speed and aggression, but I also like dynamics. You feel the power of the storm if you have that calm before and after.

People in the metal community hate Korn, but I always thought they did an amazing job of heating up and cooling down throughout a song. They'll have a 4 minute song that has more changes and movement than a lot of hour long albums.

Perfect example of buildups, breakdowns, and cooldowns. Might not be metal, but it's dynamic. It moves, changes, and does what music should, it grabs the listener:

https://www.youtube.com/watch?v=igX0ZEJKXsQ