Top panel: metallicity histograms for GES iDR5 stars (solid line), and SB1 candidates from sets 1 (red) and 2 (blue). Bottom panel: sensitivity of the global GES SB1 fraction to the metallicity combining the different spectral types of the right panel of Fig. 21 and comparison with literature results. Red and blue dots correspond to SB1 fractions of GES sets 1 and 2; the dots are centred on the median metallicity of each bin (of width 1 dex) and the metallicity range in each bin is illustrated by the horizontal error bars. Red and blue trends are almost superimposed. Yellow diamonds correspond to the SB1 fractions of Badenes et al. (2018) (see discussion in Sect. 4.4.7) centred on the median metallicities of their two samples covering a metallicity range illustrated by the yellow error bars.