States of matter are the main forms in which matter exists. The four main states are solid, liquid, gas, and plasma. Each state describes how matter appears and is grouped. All matter belongs to one of these states.

States of matter are found in different places on Earth and in space. Solids can be rocks or metal, liquids include water, and gases make up the air. Plasma is found in stars and lightning. These states are used to classify all types of matter.