Glass does not flow until you heat it up past its glass–liquid transition temperature (almost the same as a melting point, more on that shortly.) Glass has both a fixed volume and a fixed shape. The only thing that glass has in common with a liquid is that disorder of its atoms. Even then, the atoms vibrate around fixed positions, as is typical of a solid, rather than moving relatively freely as they would in a liquid.Glass is a solid.It is, however, part of a class of solids that often get neglected. It is a perfect example of an amorphous solid.