  General relativity and quantum field theory govern all fundamental physical
processes, from nuclear and subatomic scales to the solar system, galactic, and
cosmology. Both theories work remarkably well in their tested domains. However,
there is minimal overlap between the two domains. Our work demonstrates that
the non-overlapping of domains \emph{no longer} holds when non-perturbative
effects are considered. We introduce a novel mechanism in which the gravitons
acquire \emph{effective mass} due to the spontaneous symmetry breaking (SSB) of
global or local symmetry of complex scalar field minimally coupled to gravity.
In the flat space-time limit, we demonstrate that the resulting action for the
graviton is identical to the extended Fierz-Pauli (FP) action, corresponding to
the mass deformation parameter $\alpha = 1/2$. The extended FP action has 6
Degrees of freedom and no ghost. For local $U(1)$ SSB, we establish that the
effective graviton mass is related to the mass of the gauge boson and the
electric charge of the complex scalar field. Interestingly, our results
indicate that the millicharged dark matter scalar fields, generating dark
photons, can produce graviton mass of the same order as the Hubble constant
$(H_0)$. Hence, we argue that the dark sector offers a natural explanation for
the acceleration of the current Universe.
