Hey everyone, This is my first post on this forum. Please tell me if I do some mistake. :) So, there is my question ; I have search a long time on the web but I don't find any answer... Why the metallicity influences the effective temperature and the luminosity of a star ? I read somewhere that the more metallic star, the more opaque the atmosphere. Because there are more transition lines available for photons to be absorbed or something like it. But I don't see why this implies a change in luminosity or temperature. Any idea ? Thanks a million ! :) Have a nice day !