Help with tone Crate Shockwave
 

Hey, I'm just trying to get a better tone for playing Pantera, Slayer, Metallica, etc. I'm using a Crate Shockwave half stack. My settings are:
High: 9
Mid: 9
Bass: 4
Gain: 6
Shape: 3

I don't really understand what shape is though. The highs and bass are like that because it seems like this amp is really bassy. My guitar is a Carvin V220 with EMG 81/85 pickups, I usually just turn everything to 10 on the guitar. I'm thinking maybe I need an EQ pedal to help shape the tone, but I dunno, what do you guys think?