The intergalactic medium (IGM) plays a relevant role in galaxy evolution being the reservoir of gas for star formation and, at the same time, collecting the products of star formation ejected from galaxies. The IGM is studied mainly in absorption in the spectra of high redshift bright objects. In this talk, I will briefly review the recent development in the study of the IGM, in particular the determination of its metal enrichment, in the context of the baryon cycle in galaxies. I will focus my presentation on the high redshift regime, reaching the epoch of reionization, where strong constraints are set to the models of galaxy evolution.