A covalent bond is formed between two non-metals that have similar electronegativities. Neither atom is strong enough to attract electrons from the other. For stabilization, they share their electrons from outer molecular orbit with others. An ionic bond is formed between a metal and a non-metal. Non-metals(-ve ion) are stronger than the metal(+ve ion) and can get electrons very easily from the metal. These two opposite ions attract each other and form the ionic bond.