Here's why:

* Molecular Density: Solids have molecules packed tightly together. This allows sound waves to travel quickly by vibrating neighboring molecules.

* Elasticity: Solids are highly elastic, meaning they can easily return to their original shape after being deformed. This elasticity helps sound waves propagate efficiently.

Example: Sound travels faster through steel than through air.

While solids generally have the highest sound speed, the specific material and its properties (like temperature) also play a role.