The fastest guns in town are silver, tin, and copper. Aluminum is quick on the draw, too. Middling-speed substances include cast iron and carbon (rolled) steel, the type of sheet metal that is used to fashion traditional woks and crepe pans. Stainless steel ranks even lower in heat-flow efficiency.
Even poorer conductors are glass, porcelain, earthenware, and pottery in general. The sluggish attributes of these materials, however, can be a plus in serving dishes. Providing that such a vessel is covered and its walls are thick enough, it absorbs and gives up heat so languidly that it should keep your food warm for a long time.
Factors other than the type of metal also determine how evenly a pot heats food. The thicker its gauge, the more uniformly a pot will distribute heat throughout its interior surface. However, though a thicker gauge will help compensate for the mediocre heat-conducting properties of iron, the weight of the extra metal usually makes the pot unwieldy. A metal's finish also affects cooking efficiency.