What do molecules do in all substances?

Molecules in any substance are in continuous motion.
In solids, the molecules are arranged in a certain order and vibrate around the equilibrium position. The force of interaction between molecules is great, the molecule cannot leave the position of equilibrium. As a result, solids retain their shape and volume.
In liquids, the force of interaction between molecules is less than in solids. Molecules can not only vibrate about an equilibrium position, but also jump from one equilibrium position to an adjacent one. The liquid retains its volume, but does not retain its shape, these are due to the fluidity of the liquid.
In gases, the forces of interaction between molecules are negligible. Molecules are in chaotic motion and can move freely throughout the volume.