Similarities:
-They allow the union of two or more atoms.
-They both have high melting points.
-They both conduct electricty.
Differences:
-It's harder to break down a covalent bond than a ionic bond.
-Covalent bond makes atoms to share electrons, in ionic bonds it does not happen since one atom donates its electrons to the other one.
-Ionic bonds are between atoms with different charges, one anion (-) and one cation (+). Covalent bonds can be between atoms with the same charge or with different charges.