ionic bonding

Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of electrostatic attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points. 

A chemical bond formed between two ions with opposite charges. Ionic bonds form when one atom gives up one or more electrons to another atom.

NaCl:  When sodium (Na) and chlorine (Cl) are combined, the sodium atoms each lose an electron, forming cations (Na⁺), and the chlorine atoms each gain an electron to form anions (Cl⁻). These ions are then attracted to each other in a 1:1 ratio to form sodium chloride (NaCl).

A covalent bond, is a chemical bond that involves the sharing of electron pairs between atoms. 

Water, H₂O. Hydrogen atoms can each form onecovalent bond, while oxygen atoms can each form two covalent bonds. Two pairs of electrons are shared in a water molecule (H₂O).