In essence, a dative covalent bond is just a covalent bond with an unpaired electron, therefore, shared between two atoms in a delocalised manner. An example of this is Carbon monoxide, which is formed in nature by the reaction of a free radical oxygen (Free radical oxygen = with an unpaired electron) with carbon. This molecule is formed by a double bond, 4 electron shared between the two atoms, and an unpaired atom delocalised between the two, which is anotated with a fragmented line and an extra charge.