How is it possible to set a car on fire with fireworks?

I once saw this court case on judge judy where some kid set a pick up truck on fire with sparklers (apparently, he threw a few into the back part of the truck). How is it possible for a pick up truck to be set on fire in that manner? Trucks are made out of metal, not wood. Is the paint itself actually flammable? I always thought that manufacturers made vehicles out of fire resistant material.