Teleology is about functions, ends, and goals in nature. This Element offers a philosophical examination of these phenomena and aims to reinstate teleology as a core part of the metaphysics of science. It starts with a critical analysis of three theories of function and argues that functions ultimately depend on goals. A metaphysical investigation of goal-directedness is then undertaken. After arguing against reductive approaches to goal-directedness, the Element develops a new theory which grounds many cases of goal-directedness in the metaphysics of powers. According to this theory, teleological properties are genuine, irreducible features of the world.