Was Goliath a real Bible figure?

I have always believed that Goliath, of David's fame, was a true non-fictional Bible personage. I have been informed that my beliefs are totally wrong, that "angels didn't forsake their dwelling place in the heavens, and come to earth to make children with the daughters of good-looking men." I have learned that the offspring of these relations was a large man called a Nephilim. Who can shed light on this ?? I am always open to learn sharper truth!