You're confusing "literal" with face value. Obviously, when Jesus said he was the "door of the sheep" he should not be taken at face-value as if he were a piece of wood with hinges.
To take a passage "literally" means that we interpret the passage in teh light the author has in view. So when we read that God is a rock, we use the metaphor for what it is intended to mean by the author, thus we look for the literal meaning the metaphor points us to.
Nothing in what John described about Jesus was metaphorical. He did see Jesus in His glory. You can't just assign figurative devices to the text when they are not warranted. In this case, John is not using a metaphor to describe Jesus. He is simply describing what he saw.
