Many people believe that Genesis 6 :1-4 indicates that angels (sons of God) and women had sexual relations and engendered a race of giants know as the Nephilim.  They claim that these fallen hybrid beings brought much violence and destruction on the earth.  This violence and destruction was what caused God to send the flood upon the earth. Who were the "sons of God" were they fallen angels that cohabitated with women or is there another explanation? This is the first of a two part series on the sons of God.  

I have attached a link to the "Book of Enoch" that was used in this message and also a copy of the sermon notes that will help you follow along with this complex and intriguing subject.

Richard Charles. The Books of Enoch. International Alliance Pro-Publishing. 2012.

Arnold Mendez/Sermon Notes: Sons of God-Genesis 6 Part 1