From verse 1 we learn that one of them was the Lord. The "he" is Abraham. That leaves two others. In chapter 19:1, if we would read through the whole chapter there would be no break here, it says,
Those are the other two who were with the Lord when He was entertained by Abraham. So the other two "men" are identified as angels. Here Abraham is entertaining three spirit beings and it is interesting that the story begins as though they just suddenly appeared, like one moment he couldn't see them and the next moment there were suddenly three people there. Apparently Abraham was of such experience that he recognized immediately who they were and that he was not nonplussed because he immediately bowed down and worshipped one of those spirit beings because he recognized that One as the Lord.
We're going to look at what the Bible writers state concerning what they and others saw of God with their natural eyes. We're going to begin back in the book of Genesis; right where it seems everything begins.
Let's just review those verses and look at what it says. First of all, the Lord appeared and Abraham saw Him with his eyes and what did He look like? He looked like a man. But it was the Lord because Abraham bowed down and worshipped Him and He didn't reject the worship.
In verse 4, Abraham said, "Let a little water be brought, and wash your feet." God has feet. "And I will bring a morsel of bread." We find that God took the bread and the meat and the three of them ate. He spoke, so He had a voice and He conversed with them. That's pretty clear.