In my game the players left arm is this weird transparent color, but the right is normal. When i drag the right arm's material over to the left it doesn't fix the problem, so there's something wrong with the object itself not the material. How do i fix this?
3D models are usually rendered only on the outside or inside of the model, the reason the right arm is partially transparent is probably because during the 3d modelling process the right arm had its faces flipped so that when rendered in unity the arms inside faces are the only faces that render hence the reason you can see the back and not the front. I know in particular blender renders both sides which can confuse people when they import their models into unity and see only one side of the face rendered.
I don't know what 3d modelling software you use but if you look online you should find a tutorial on how to invert the drawn faces, this may solve your problem.