The ability of materials to act as conductors and insulators is relative. All materials, even those that are commonly classified as insulators, still allow some conduction of heat. For example, ceramic is a better conductor than Styrofoam. A ceramic mug filled with hot water feels warmer in your hand than a Styrofoam cup filled with hot water. However, ceramic is a worse conductor than metal. A metal mug filled with hot water would feel even hotter than the ceramic mug.