Ionic bonding occurs between metallic and non-metallic atoms. Electrons are transferred from metal atoms to non-metal atoms. This results in positively charged metal ions and negatively charged non-metal ions and thus, an ionic bond. KEY PHRASE: transfer of electrons. Covalent bonding occurs between non-metallic atoms. Pairs of electrons are shared between the non-metal atoms, so that each atom has a full shell of electrons. This creates a covalent bond. KEY PHRASE: sharing of electrons. Metallic bonding occurs between metallic atoms. The electrons in the outer shell of non-metal atoms become delocalisedto move freely throughout the structure of the metal. The metallic structure is held together by the strong electrostatic forces of attraction between the delocalised electrons and positively charged metallic ions, creating a metallic bond. KEY PHRASE: electrostatic forces of attraction.