Similarities:- Both ionic and metallic crystals are hard in nature due to the good force of attraction between molecules. Both have fairly high melting points. In both ionic and metallic bond is non-directional.
Differences:- In ionic solids, attractive forces are coulombic or electrostatic whereas in case of metallic solids forces attractive forces are metallic bonding.
Moreover, ionic solids are insulators in the solid state whereas metallic solids are a very good conductor of electricity in both solid and molten state.