  We interpret the recent NANOGrav results in terms of a stochastic
gravitational wave background from metastable cosmic strings. The observed
amplitude of a stochastic signal can be translated into a range for the cosmic
string tension and the mass of magnetic monopoles arising in theories of grand
unification. In a sizable part of the parameter space, this interpretation
predicts a large stochastic gravitational wave signal in the frequency band of
ground-based interferometers, which can be probed in the very near future. We
confront these results with predictions from successful inflation, leptogenesis
and dark matter from the spontaneous breaking of a gauged B-L symmetry.
