what somebody is made of

what (one) is made of

One's true talent, fortitude, ability, courage, or worth, especially in the face of adversity or difficulty. No one thinks you stand a chance in this match, but you go out there and let them see what you're made of! This could be the biggest trial of my career. Time to go show what I'm made of!
See also: made, of, what

what somebody is ˈmade of

(informal) how somebody reacts in a difficult situation: Let’s see what he’s made of.Go out and show them what you’re made of (= show them that you are strong, intelligent, etc.)!
See also: made, of, somebody, what