As the title states I've been struggling with trying to get a relaxed and clean picking motion. I play in a metal band so getting a clean and fluid picking technique down is something that is really important to me and to the music my band plays.

I have tried countless videos/tutorials/pick grips and nothing seems to be helping me evolve past this really stiff style I've developed from years of bad habits. at this point even resting my hand on the guitar causes my hand to shake because all my muscles in my fore arm and wrist just seem to lock up.

The thing that I find most troubling is I feel more relaxed in my playing at faster tempos then slow that being said I'm sure that i just not noticing uneven picking because of the speed and it also lacks control.

any pointers that someone can offer would be greatly appreciated. I'm just not sure what else there is to try at this point.
I suffer from this issue as well. So I'd be happy to hear what people have to say.
Shit man, if your arm locks up when your just resting it on the guitar not even playing! then you may have damaged something, go and speak to a doctor. your arm, wrist and hand should be relaxed. If you have been playing like this for years you will need to relearn your picking technique from scratch, play simple things slowly, if you feel any tension stop and shake it out.
You need to relearn your picking technique.

First off get a good grip of the pick, which is mainly making sure you are holding the pick with the absolute minimum amount of tension. If your picking hand is stiff then you are exerting too much tension somewhere in your arm, most likely the fingers holding the pick, the forearm or the shoulder in my experience.

You need to pick with small, efficient motions while staying completely relaxed. The relaxation part is by far the most important part when reprogramming your technique, but it's also incredibly important to minimize your movements. If you are able to completely relax yourself when playing you'll find that you will have a much easier time playing with small quick motions.

For a while you're going to have to slow down, and I mean really slow down to the point where you aren't even playing with a metronome. Pick a very simple picking lick to begin with, and focus only on making sure you can make every note sound while playing with complete relaxation and somewhat small motions. This speed is probably going to be a lot, lot lower than you'd expect/like but don't worry; everyone with good technique on guitar spends a lot of time practicing super slowly. If you tense up while playing, immediately stop and relax yourself; you can try hanging your arms in their natural position for a few seconds for example.

The point is you want to train yourself to play without tensing up which will fix your picking hand feeling stiff. It's not something that is going to happen overnight but if you put in a good 30 minutes to an hour practicing this a day then you will see results within a few weeks and after a few months you will be much, much better off than you are now.
Was in same boat until pretty recently. Relearn picking technique is what you gotta do and go all the way back to basics. Go slow as hell and play your typical basic riffs, play from wrist, be conscious of bicep and the other forearm muscles tensing up. Like if it feels you're using those, just stop and adjust. This tense technique, least the one I used, made playing pretty sloppy overall - and things like playing faster+changing strings a lot, never seemed to become consistent no matter how much I practiced and whether or not I hit all the notes was more determined by chance than control. Changing picking technique from that has done wonders for me, I still may slip back into old ways occasionally but am conscious about it when it happens. This can definitely be done.
There's a preassumption when learning metal guitar, that since it sounds so damn heavy and hard, you might naturally approach it playing really hard and aggressive as well. Took a long time to realize that's not the case at all.