typically have much higher melting points than molecular .
Ionic compounds are held together by electric attractions between positive and negative ions. These are ionic bonds, and these bonds keep the ions together in a regular 3-d pattern (a crystal lattice)
To melt an ionic substance, you have to disrupt these bonds. This requires a lot of energy.
Molecules are held together by covalent bonds, which are strong. But you do not need to break these covalent bonds when melting a molecular substance. In molecular solids, each molecule is neutral and it is attracted to its neighboring neutral molecule by an intermolecular force (3 types: dispersion forces, dipole-dipole force, and hydrogen bonding).
To melt a molecular substance, you need to break these weak intermolecular forces between neutral molecules, which is why ionic compounds generally have much higher melting points than molecular compounds.