Why do many metal ions produce acidic solutions when dissolved in water?

Water molecules form a complex with metal ions (usually a 6-coordinate complex). And the high charge density on a metal ion draws electrons away from the water molecules, making the O-H bonds more polar than normal. This allows the dissociation of the protons, making solutions of most metal ions acidic

Idon't mean to be a smart alec, length of atoms' bonds is the simplest way to define it.