Which one of the three bond types distinctly different form the other two? explain why so?

The metallic bond is distinctly different from covalent and ionic bonds. Metallic bonding involves atoms sharing electrons among many atoms. Covalent and ionic bonds depend on the electronegativity differences between atoms and the sharing of electrons to a greater or lesser extent between just a few atoms. 

The closer the atoms are to becoming ionic the more highly dense the negatively charged side gets.

Answer two atoms of oxygen;