Both the Bible and good philosophy report that God is non-physical - spirit. In John 4:24 it is said that God is spirit (see also Luke 24:39; Romans 1:20; Colossians 1:15; 1 Timothy 1:17). This is why no material thing was to be used to represent God (Exodus 20:4). But this can also be shown by reflecting on what God is. Philosophically the same truth comes through. All that is created is necessarily finite and limited. But the first cause (God) is uncreated, and therefore must be non-finite, or infinite. That which is beyond the finite must, by definition, be infinite, and the Bible states that God is beyond creation (1 Kings 8:27; Job 11:7-9; Isaiah 66:1-2; Colossians 1:17). That which is physical cannot be infinite - for you cannot add finite parts together until they reach infinity. Therefore God is spirit as opposed to physical/material in His Being. This does not mean He cannot localize a physical appearance. God is not composed of matter nor any other imaginable substance. He also cannot be measured, is not spatial, and has no true location (presence is a different concept).
Knowing this truth can help us understand the metaphorical speech often used to describe God or, more often, God’s actions in Scripture. In the case of God, once all finitude is negated from a statement, what is left is what is actually true. If nothing is left, then it is a pure metaphor. Some metaphors use attributes from creation itself (2 Samuel 22:3). Others use man’s attributes (anthropomorphism - Deuteronomy 33:27). In this way we can go from what we know by experience to what we know through the metaphors. For example, when Scripture describes God’s mighty arm we know that arms are by definition limited - but might is not. So God’s mighty arm is actually unlimited power to act (what we call omnipotence). When Scripture describes God’s mind, we know that minds are limited, but knowledge is not. God’s mind is actually His infinite knowledge (what we call omniscience).
There were times in the Bible when God appeared in a physical body in order to be seen by men in a form which they could perceive without danger to themselves. Because God said, “No man can see me and live” (Exodus 33:20), He chose at certain times to reveal Himself in human form. These occurrences are called theophanies (Genesis 12:7-9; 18:1-33; 32:22-30). Every theophany wherein God takes on human form foreshadows the incarnation, where God took the form of a man to live among us as Emmanuel, “God with us” (Matthew 1:23).