Distribution of GW progenitor events as a function of the metallicity of the parent stellar particle in the MTNG740 simulation. The metallicity distribution of the total merger events, along with the contributions from different compact binary merger channels, is displayed as indicated in the legend. All distributions are normalized to the total number of merger events (i.e., N_tot = BBH + BHNS + BNS), so that each metallicity bin represents the fractional contribution of that specific metallicity to the overall number of events. As in Fig. 6, the vertical dashed line marks the value of Z_⊙ adopted in MTNG.