They were angels, messengers.
I'll concentrate on Gen 18 and quote some verses for you to explain how they refer to angels. Can one seriously conclude that Yahweh was absent?
1 Yahweh appeared to Abraham by the oak trees belonging to Mamre as he was sitting at the entrance of his tent during the hottest part of the day.
3 He said, “
My Lord, if I have found favor in Your sight, do not pass by Your servant.
10
Yahweh said, “I promise I’ll come back to you next year at this time, and your wife Sarah will have a son.” Sarah happened to be listening at the entrance of the tent, which was behind him.
13
Yahweh asked Abraham, “Why did Sarah laugh and say, ‘Can I really have a child now that I’m old?’
15 Because she was afraid, Sarah denied that she had laughed. But
Yahweh said, “Yes, you did laugh.”
17
Yahweh said, “I shouldn’t hide what I am going to do from Abraham.
20
Yahweh also said, “Sodom and Gomorrah have many complaints against them, and their sin is very serious.
22 From there the men turned and went on toward Sodom, but Abraham remained standing in front of
Yahweh.
26
Yahweh said, “If I find 50 innocent people inside the city of Sodom, I will spare the whole place for their sake.”
28 what if there are 45 innocent people? Will you destroy the whole city because of 5 fewer people?”
Yahweh answered, “I will not destroy it if I find 45 there.”
33 When
Yahweh finished speaking to Abraham, he left. Abraham returned home.