Imovie Audio Problem.

Hello, I have been recording some covers on my electric guitar using garajebann for quite awhile now, but i've noticed a big problem. The built in mic distort the sound soo much. I've tried normalizing, but it really doesn't help much. I think it has to do with that fact that it compensates a lot. Please let me know if theres any way to fix this. If not, I guess I'd have to buy a mic. Anyone know of a good mac mic for recording electric guitar?