In a solid, the atoms, molecules, or ions are held together by strong intermolecular forces. These forces can be classified into three main types:

- Covalent bonds: These bonds are formed by the sharing of electrons between atoms. They are the strongest type of intermolecular force.

- Ionic bonds: These bonds are formed by the attraction between positively charged ions and negatively charged ions. They are also very strong.

- Metallic bonds: These bonds are formed by the attraction between positively charged metal ions and a "sea" of delocalized electrons. They are not as strong as covalent or ionic bonds, but they are still strong enough to hold metals together in a solid state.

The strength of the intermolecular forces in a solid determines its melting point. The higher the melting point, the stronger the intermolecular forces.