  We report on a study of the density response in doped Weyl semimetals or Weyl
metals in the presence of an external magnetic field. We show that the applied
field leads to a contribution to the density response, which is topological in
nature and is closely related to the phenomenon of chiral anomaly. This
contribution manifests in a nonanalytic nonclassical correction to the
electronic compressibility and the plasmon frequency, proportional to the
magnitude of the magnetic field. Such a nonanalytic correction to the
electronic compressibility is a smoking-gun feature of Weyl metals, which
clearly distinguishes them from ordinary ferromagnetic metals.
