Mgo (Magnesium oxide ) has ionic bonding . NOT covalent bonding Or metalic bonding.Watch
+2 charge on it and oxide ion will have a -2 charge on it) the electrostatic attraction between these two ions are said to be the Ionic Bond. Another evidence for this will be the "electron density plot" . this electron density plot will show ZERO electron density between Mg(+2) ion and Oxide (-2) ion. so Again we can come to a conclusion that Mgo consist an ionic bond ,not a covalent bond.