Chuck Missler is just one of many who adopt the angel view (rather than the Sethite view). He certainly didn't invent it.
I don't want to start a huge discussion. But I am curious...what is your explanation of the existence of giants in the Bible?
The bible clearly states the giants were large human beings, it's that simple
A Cubit = 18"
King OG had a bed made of iron that was 13 feet long, and 6 feet wide, a big human
Deuteronomy 3:11-13KJV
11 For only Og king of Bashan remained of the remnant of giants; behold his bedstead was a bedstead of iron; is it not in Rabbath of the children of Ammon? nine cubits was the length thereof, and four cubits the breadth of it, after the cubit of a man.
12 And this land, which we possessed at that time, from Aroer, which is by the river Arnon, and half mount Gilead, and the cities thereof, gave I unto the Reubenites and to the Gadites.
13 And the rest of Gilead, and all Bashan, being the kingdom of Og, gave I unto the half tribe of Manasseh; all the region of Argob, with all Bashan, which was called the land of giants.
Goliath was about 13.5 feet tall, bigger than the King of Og, both "Human Men"
1 Samuel 17:4KJV
4 And there went out a champion out of the camp of the Philistines, named Goliath, of Gath, whose height was six cubits and a span.