  A graviton of a nonzero mass and decay width propagates five physical
polarizations. The question of interactions of these polarizations is crucial
for viability of models of massive/metastable gravity. This question is
addressed in the context of the DGP model of a metastable graviton. First, I
argue that the well-known breakdown of a naive perturbative expansion at a low
scale is an artifact of the weak-field expansion itself. Then, I propose a
different expansion -- the constrained perturbation theory -- in which the
breakdown does not occur and the theory is perturbatively tractable all the way
up to its natural ultraviolet cutoff. In this approach the couplings of the
extra polarizations to matter and their selfcouplings appear to be suppressed
and should be neglected in measurements at sub-horizon scales. The model
reproduces results of General Relativity at observable distances with high
accuracy, while predicting deviations from them at the present-day horizon
scale.
