This week's parsha's opening scene has God appearing to Avraham as he sits at the door to his tent in the heat of the day. The next verse describes how three men approached him. The classic interpretation, which even has major ethical implications, is that Avraham interrupted his conversation with God in order to attend to guests.
Rashbam has a radically different interpretation. He says that the first verse is a 'headline', and the later story fleshes it out. In other words, he says that God appeared to Avraham - as described in the first verse - in the guise of three men - as described in subsequent verses. He sticks with that interpretation throughout the episode, even refining it somewhat. He says that 'God' in this episode speaks through the 'greatest' of the visitors. It is He who remains to speak with Avraham as the other two go to destroy Sodom. Looking at verses 21 and 22 of the chapter, it seems that when God says 'I will go down to see if they have acted as has been screamed' it prompts the other 2 'men' to leave for Sodom, while the third remains to converse with Avraham.
This gives a really interesting perspective on what angels are. It's almost like the 'agents' in the first Matrix movie, the form used by the matrix itself, the program which contains all within it, to appear to entities which exist in the program.