After fainting, metallic taste in mouth?

Last night my husband was having bad stomach cramps. He went to the bathroom to have a bowel movement, and while there, he fainted. I heard the crash and ran to help. After what seemed like forever, he came to, and we got him up, let him rest, then he moved to the couch. I had him go to the ER to get checked out, which they found nothing... anyway, my question for you is: when he came from the bathroom, he mentioned he had a 'metal taste' in his mouth. I've heard of this before, but can't think of what it was I heard it could be. The Dr. at the ER didn't seem too concerned, but if you have any idea, I'd like to hear what it could have possibly meant. Thanks for your time...