God claims to be a shepherd. He designed sheep in his creation to be looked after by a human being. Nobody has said, "You know, God is kinda like a shepherd," hoping their analogy is pretty accurate. Rather, God himself has said, "What you see in a good shepherd doing his job, see that in me."

And it's a metaphor of course. We don't need green pastures or still waters or a comforting rod and staff. Rather, we need things like those, the providence and protection that a shepherd provides. God metaphorically leads us to green pastures and peaceful waters, metaphorically directs us through gloomy dark valleys inhabited by jackals and wolves.