Lutetium is a chemical element that belongs to the group known as rare earth metals. It is very similar to the other elements in this group, but it is the last one in the series. Lutetium is a soft, silvery-white metal that is easily cut with a knife. It has the highest density and melting point of all the lanthanide elements. Lutetium is used in various applications, including in medical imaging, nuclear reactors, and electronic devices.