Particles in solid are closely packed and vibrate at about a fixed point and have very strong forces of attraction between them.
In liquids and gases the forces between the particles is weaker than forces between particles of solid. The particles in gases can move freely as the forces of attraction between particles are almost negligible. In liquid, particles can slip and slide over each other.
Basically solids have a more regular arrangement. Stronger forces of attraction and vibrate at about a fixed point.