Electrostatic attraction

Each involves electrons and electrostatic attraction: opposite electric charges attract. The key difference is whether electrons are transferred from one atom to another, shared as pairs between atoms, or delocalised across a metal.

The negatively charged bonding electrons are attracted to the positively charged nucleus of each atom. This strong electrostatic attraction between the shared pair of electrons and both nuclei holds the atoms together and is the covalent bond.

Electron transfer explains the formation of the ions; the ionic bond is the electrostatic attraction between oppositely charged ions.