Covalent bonds are usually distinguished from ionic bonds. The big difference between them is that while covalently bonded substances can dissolve in polar solvents (such as water), they retain their molecular form once dissolved.

Ionic bonds by contrast break when the substance dissolves. You can tell whether a substance dissolving is covalently bonded or ionically bonded because the ions are electrically charged: water containing dissolved ions conducts electricity, and water containing only dissolved covalently-bonded material does not.