What metaphors are used in Things Not Seen by Andrew Clements?

In Chapter Two, Bobby's father indicates that he sees his son as a metaphor of the Stealth Bomber...... an airplane that is supposed to be invisible. The Stealth Bomber is invisible to current radar systems, but when it passes under the sun, it still casts a shadow on the Earth. He compares the Stealth Bomber's shadow to the shadow Bobby casts on his desk when he passes his hand under the lamp light. Bobby's dad infers that there is a reason why Bobby is invisible to himself and to his parents, yet still casts a shadow.