  We establish the nonclassicality of continuous-variable states as a resource
for quantum metrology. Based on the quantum Fisher information of multimode
quadratures, we introduce the metrological power as a measure of
nonclassicality with a concrete operational meaning of displacement sensitivity
beyond the classical limit. This measure belongs to the resource theory of
nonclassicality, which is nonincreasing under linear optical elements. Our
Letter reveals that a single copy, highly nonclassical quantum state is
intrinsically advantageous when compared to multiple copies of a quantum state
with moderate nonclassicality. This suggests that metrological power is related
to the degree of quantum macroscopicity. Finally, we demonstrate that
metrological resources useful for nonclassical displacement sensing tasks can
be always converted into a useful resource state for phase sensitivity beyond
the classical limit.
