Anodized aluminum: "This material, strengthened by a coating of aluminum oxide, takes time to warm up, but it evenly disperses heat throughout the pan," says Daniel Choi, Ph.D., a professor of metallurgy at the University of Idaho, in Moscow. Anything that’s meant to cook slowly will benefit from an anodized-aluminum pot.
Cast iron: “No kitchen is complete without a cast-iron skillet,” says Food Network host and cookbook author Paula Deen. “Mine has always worked just as hard as I work.” Cast iron gives a terrific sear to meats. Even slower to heat up than anodized aluminum (you’ll need to pre-heat it on a medium-low flame for a minute or two), it maintains steady heat long after the burner is turned off, which works well when you want to keep foods warm. Many are sold preseasoned (the surface has been treated with a layer of cooked-on vegetable oil), but you can also season a pan at home. Just follow the manufacturer’s instructions.
Copper: Although pricey, "copper pots retain heat beautifully, which is invaluable when you’re attempting a tricky cooking technique, like making candy," says Jacob Maurer, a buyer for the housewares chain Sur La Table. Most copper is sold “tinned,” a process that grafts a thin layer of a metal, like stainless steel, onto the copper. This keeps the copper from leaching into food and reacting with acids, such as vinegar. The lining will last 10 to 20 years before it needs to be replaced by a metalworking pro; the copper itself will last a lifetime.
Stainless steel: It’s “rust-free, stain-resistant, and stable under extremely high temperatures,” says Choi. However, the temperature of stainless steel can vary greatly over the surface of the pan. To compensate, some manufacturers build in a copper or aluminum core. If you see stainless designated “10/18,” take that as a sign of quality. It means 10 percent of the material is nickel, which is the optimal amount of nickel available for stainless (the higher the amount, the better―nickel is typically what makes stainless steel shiny), and 18 percent is chromium, which helps prevent corrosion.