I know the reasons that diamonds are stronger than covalent materials and ionic compounds. The former is weaker because there are intermolecular forces and the latter is weaker because if pressure is applied like charged ions would be forced together making it brittle. However, I cannot think why metal substances are weaker than diamonds other than that metallic bonding is a weak bond. Can someone explain this to me? I think that ionic bonds are as strong as covalent bonds, is this true?