  We have calculated the photonic band structures of metallic inverse opals and
of periodic linear chains of spherical pores in a metallic host, below a plasma
frequency $\omega_{\text{p}}$. In both cases, we use a tight-binding
approximation, assuming a Drude dielectric function for the metallic component,
but without making the quasistatic approximation. The tight-binding modes are
linear combinations of the single-cavity transverse magnetic (TM) modes. For
the inverse-opal structures, the lowest modes are analogous to those
constructed from the three degenerate atomic p-states in fcc crystals. For the
linear chains, in the limit of small spheres compared to a wavelength, the
results are the "inverse" of the dispersion relation for metal spheres in an
insulating host, as calculated by Brongersma \textit{et al.} [Phys.\ Rev.\ B
\textbf{62}, R16356 (2000)]. Because the electromagnetic fields of these modes
decay exponentially in the metal, there are no radiative losses, in contrast to
the case of arrays of metallic spheres in air. We suggest that this
tight-binding approach to photonic band structures of such metallic inverse
materials may be a useful approach for studying photonic crystals containing
metallic components, even beyond the quasistatic approximation.
