Most metals expand when heated and contract when cooled. This is often explained using the kinetic molecular theory; when you add heat, it gives the metal atoms more kinetic energy so that they can move farther apart. As it happens, antimony and bismuth, and some of their alloys, do contract on heating and expand on cooling, but this is the exception, not the rule. Metals expand on heating and contract on cooling. This happens because each molecule can vibrate more when it's given (heat) energy. You are right, heat causes metal to expand, cold contracts it. It expands on heating and contracts on cooling.