  We consider possible observational consequences of dust and metals in \lya
forest clouds. We relate the dust content, $\Omega_d^{Lya}$, to the metal
evolution of the absorbers and assume that dust is heated by the ultraviolet
background radiation and by the CMB. We find that the dust temperature deviates
from $T_{CMB}$ by at most 10% at redshift $z=0$. The \lya cloud dust opacity to
redshift $\sim 5$ sources around the observed wavelength $\lambda_0 \sim 1
\mu$m is $\sim 0.13$, and could affect observations of the distant universe in
that band. The expected CMB spectral distortions due to high-$z$ dust in \lya
clouds is $\sim 1.25-10$ smaller than the current COBE upper limit, depending
on the metallicity evolution of the clouds. If \lya clouds are clustered, the
corresponding CMB anisotropy due to dust is $\sim 10^{-1}$ on angular scales
$\theta \simlt 10''$ at frequencies probed by various future/ongoing FIR
missions, which makes these fluctuations potentially detectable in the near
future. Emission from CII fine-structure transitions could considerably
contribute to submm range of the FIR background radiation. Depending on the
ionization of carbon and on the density of metal enriched regions, this
contribution can be comparable with the observed residual flux at
$\lambda\approx 0.15$ mm, after CMB subtraction. We argue that constraints on
metal evolution versus redshift can be obtained from the observed flux in that
range.
