What metaphors are used in Going After Cacciato by Tim O'Brien?

Metaphor:

"He believed, like Doc Peret, that somewhere inside each man is a biological center for the exercise of courage, a piece of tissue that might be touched and sparked and made to respond, a chemical maybe, or a lone chromosome that when made to fire would produce a blaze of valor that even the biles could not extinguish. A filament, a fuse, that if ignited would release the full energy of what might be. There was a Silver Star twinkling somewhere inside him."