  Clusters of galaxies allow a direct estimate of the metallicity and metal
production yield on the largest scale so far. The ratio of the total iron mass
in the ICM to the total optical luminosity of the cluster (the iron
mass-to-light-ratio) is the same for all clusters which ICM is hotter than
$\sim 2$ keV, and the elemental proportions (i.e. the [$\alpha$/Fe] ratio)
appear to be solar. The simplest interpretation of these evidences is that both
the IMF as well the relative contributions of SN types are universal. Currently
available abundances in cooler clusters and groups are much more uncertain,
possibly due to insufficiently accurate atomic physics data for multi-electron
ions, or to the ICM being multi-phase, or to a combination thereof. This
uncertainty automatically extends to the reality of radial abundance gradients
so far reported in cool clusters. It is emphasized that most metals reside in
the ICM rather than in galaxies, which demonstrates that energetic winds
operated early in the evolution of massive galaxies, the likely producers of
most metals now in the ICM. The ICM metallicity is also used to set a
semiempirical constraint of $\sim 0.1$ keV per particle to the ICM {\it
preheating} due to supernova driven galactic winds. A lower limit of the
universe global metallicity at $z=3$ is also mentioned.
