Present-day stellar (including remnants) mass–metallicity relation for galaxies with different constant SFRs over a time-span of 13.6 Gyr, adopting g_conv = 0.10 (red line) and g_conv = 0.25 (blue line), within the IGIMF-2021 context. The green stars refer to dwarf galaxies of the Milky Way and M31 galaxies (Table 4 of Kirby et al. 2013). The solid black line shows the median while the dashed lines show the 16th and 84th percentiles of the metallicity distribution of galaxies in the Sloan Digital Sky Survey Data Release 2 (Table 1 of Gallazzi et al. 2005). Note that the shown stellar masses of Kirby et al. (2013) and Gallazzi et al. (2005) are derived for the canonical gwIMF but the simulated mass–metallicity relations (red and blue lines) refers to a varying gwIMF within the IGIMF theory (see text).