Covalent bondbond in which one or more pairs of electrons are shared by two atoms.
Ionic bondbond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other. 
Metallic bonds are a special category of covalent bonds, which (unsurprisingly) occur in metals.  In metallic bonding, the electrons delocalize, forming a sort of "cloud" or "soup," interspersed with the individual nuclei. 
 Ionic bond: it is also called "electrovalent bond". It is "a type of chemical bond that can often form between metal and non-metal ions through electrostatic attraction"; 

Covalent bond is a form of chemical bonding, "characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds"; 

Metallic bond: "the chemical bond, which is characteristic of metals, in which mobile valence electrons are shared among atoms in a usually stable crystalline". 
1 5 1