Solid is a state of matter with a fixed shape and a fixed volume. Solids keep their shape and do not flow like liquids or gases. They can be hard or soft, heavy or light. Common solids include rocks, wood, and metal.

Solids are found everywhere on Earth in both natural and human-made materials. Buildings, tools, and many everyday objects are solids. Solids are part of many environments, from mountains to homes. They are one of the main forms of matter.