"Copper is famed for its ability to conduct heat and electricity—it's no accident that it's copper and not iron that runs through the electrical wires in our walls—and it's this quality that makes it such an interesting metal for cooking.
Copper inverts these rules. It heats quickly and evenly, but it loses that heat just as fast. This responsiveness gives it a nimbleness and agility that can be very useful for delicate proteins like fish and seafood, as well as sauces, caramel, and chocolate—remove a copper saucepan holding a delicate sauce from the heat and its temperature will drop rapidly, reducing the chances the sauce overcooks or breaks from exposure to the retained heat in the metal."
Daniel Gritzer, Serious Eats