It seems like there are two different story lines in this chapter, and I guess in some ways, that might be true. However, the continuity and emphasis of the encounter is striking to me.
The chapter begins with these powerful words, "The LORD appeared unto [Abraham]... and he lift up his eyes and looked, and, lo, three men stood by him: and when he saw them, he ran to meet them from the tent door, and bowed himself toward the ground." Dubbed a theophany (an appearance of God in a visible form), this was a communion like none before or since. Abraham begged these three, My Lord, if now I have found favor in Thy sight, pass not away, I pray Thee, from Thy servant." Abraham went on to set a feast before these three men" and stood by "Them" under a tree while "They" ate.
Now, perhaps we could "go to town" discussing God's repeated promise to Abraham concerning a son, or Sarah's laughter and denial, or Abraham 's courageous banter with God concerning the destruction of Sodom... but what intrigues me most is the simple fact that God was there communing with him at all.
Imagine God saying, "Shall I hide from Abraham that thing which I do... for I know him..." And, imagine Abraham "drawing near" to God (as is recorded in this chapter). There was obviously much more to all of this than a baby forecast, sin city and Abraham's six stage prayer for mercy for his nephew. God was COMMUNING with a friend! Verse 33 states it plainly: "And the LORD went His way, as soon as He had left communing with Abraham.” WOW! Abraham was indeed the friend of God! (2 Chronicles 20:7 & James 2:23)