Even though metals constitute only a few per cent of the total mass fraction of stars, they have a huge impact on the way stars and galaxies evolve. In that respect, metallicity in the Universe is, like the salt in a dish, a small amount that can completely change its flavour!

The metal-rich stars have never attracted as much attention as the metal-poor halo stars, which tell us about the first supernovae and the early chemical evolution of our Galaxy. However, metal-rich stars are of interest in their own right and can shed new lights on very topical subjects. For instance, it is now well established that stars rich in metals are more likely to harbour giant planets. This awareness has elicited careful and detailed abundance studies of ever more metal-rich stars. As a byproduct, trends of the abundances of many elements at high metallicity are now available and await an interpretation in terms of stellar nucleosynthesis and chemical-evolution models. The extent to which these observed trends are in line with what is expected from the current stellar and chemical-evolution models largely remains to be checked and this is one of the main topics of these proceedings.

Putting the subject into a larger context, let us recall that the attainment of adequate models of the high-metallicity regime is of great interest for the study of the central regions of galaxies, which are thought to have higher-than-solar metallicity. Also, it appears that many quasar environments are metal-rich out to redshifts of at least 5.