The quantum and classical descriptions of an electro-magnetic field are connected by the correspondence principle. We consider the electromagntic field as a source for gravity and compare the metrics due to a classical and quantized electromagnetic field. The quantization of the source demands the quantization of gravity. We also show that (i) the conformal degree of the freedom isnot an unphysical mode, and (ii) quantum gravitational effects can exist even when the light cones do not fluctuate.