Because of the nature of ionic and covalent bonds, the materials produced by those bonds tend to have quite different macroscopic properties. The atoms of covalent materials are bound tightly to each other in stable molecules, but those molecules are generally not very strongly attracted to other molecules in the material. On the other hand, the atoms (ions) in ionic materials show strong attractions to other ions in their vicinity. This generally leads to low melting points for covalent solids, and high melting points for ionic solids. For example, the molecule carbon tetrachloride is a non-polar covalent molecule, CCl4. It's melting point is -23°C. By contrast, the ionic solid NaCl has a melting point of 800°C.
Ionic Compounds

Crystalline solids (made of ions)
High melting and boiling points
Conduct electricity when melted
Many soluble in water but not in nonpolar liquid
Covalent Compounds

Gases, liquids, or solids (made of molecules)
Low melting and boiling points
Poor electrical conductors in all phases
Many soluble in nonpolar liquids but not in water