Solids represent the state of matter in which atoms are very tightly bound to each other. Other states of matter are liquid and gases. In the case of liquids, the atoms are somewhat loosely bound to each other. That is why liquids tend to take the shape of the container in which they are poured. Gases have the loosest packing of atoms, as compared to solids and liquids and that is why gases have no specific physical shape or structure.
In solids, atoms are tightly bound giving a rigid and a specific shape to the matter. That is the reason solids retain the shape irrespective of the container they are stored in. Some examples of solids are metal fragments, bricks, rocks, plastic, nails, wood, etc.
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