What forces hold molecular solids together?

Molecular solids  are held together  by  intermolecular forces (IMFs)

EXPLANATION:

Intermolecular forces (IMF) are  forces which enhance the  interaction  between  the molecules, like forces of repulsion  or attraction that acts between  the molecules and other types of  particles, e.g., ions or atoms.  Intermolecular forces are of three types .They are

Dipole-dipole interaction:  

The force that occurs when partially oppositely charged ions interacts with the neighbouring molecules  

Hydrogen bonding:  

It is a special kind of dipole-dipole interaction  that takes place in hydrogen atom bonded either  to an oxygen, nitrogen, or fluorine atom.

 London Dispersion attraction:

This is  the weakest among   intermolecular forces. This  exists  between all different  types of molecules that are either ionic , covalent-polar or nonpolar.