  We propose that we can realize "tight-binding photonic bands" in
metallophotonic waveguide networks, where the photonic bound states localized
around the crossings of a network form a tight-binding band. The formation of
bound states at the crossings is distinct from the conventional bound states at
defects or virtual bound states in photonic crystals, but comes from a photonic
counterpart of the zero-point states in wave mechanics. Model calculations show
that the low-lying photon dispersions are indeed described accurately by the
tight-binding model. To exemplify how we can exploit the tight-binding analogy
for a {\it designing} of photonic bands, we propose a "flat photonic band" in
the kagome network, in which the photonic flat band is shown to arise with
group velocities that can be as small as 1/1000 times the velocity of light in
vacuum.
