Metis is the innermost moon of Jupiter, also known as Jupiter XVI; it is a small object of uneven shape. Together with Adrastea, Metis orbits inside the synchronous orbit radius of Jupiter, which means that it orbits faster than Jupiter rotates on its axis. As a result, its orbit will eventually decay and Metis will fall into the planet. Metis and Adrastea also circle around inside Jupiter's main ring and are undoubtedly the source of the material in this ring.