The statement “God is our Father” means that God is like a  human father. In other words, God is analogous to a father. In  some ways he is like a human father, and in others he is not.  There are genuine points of similarity as well as genuine points  of dissimilarity. Like all analogies, the analogy of God as Father breaks down at points. However, it is still an extremely useful and vivid way of thinking of God.