Absorption systems observed along the line of sights to distant quasars are observed at all redshifts and the full range of the electromagnetic spectrum is needed to recover the variety of transitions of different elements. However, some important elements are found within the Lyman forest and their absorption line profiles need to be analyzed against the presence of possible Ly- α contamination. Considering the cosmological evolution of the number density of hydrogen clouds, the probability to detect uncontaminated metal lines is higher in the UV-Optical region exploited by CUBES. The list of these elements includes some important ones such as D, H 2 , O  i , N  i , O  vi , Ar  i , P  ii , C  ii , S  ii and B  ii . The determination of some of them in the Damped Ly- α galaxies and their astronomical interest are briefly discussed.