  We discuss the physical interpretation of stress-energy tensors that source
static spherically symmetric Kerr-Schild metrics. We find that the sources of
such metrics with no curvature singularities or horizons do not simultaneously
satisfy the weak and strong energy conditions. Sensible stress-energy tensors
usually satisfy both of them. Under most circumstances these sources are not
perfect fluids and contain shear stresses. We show that for these systems the
classical double copy associates the electric charge density to the Komar
energy density. In addition, we demonstrate that the stress-energy tensors are
determined by the electric charge density and their conservation equations.
