We present metallicities and their variations with different parameters for 36 high-latitude fields covering Galactic longitudes 0° < l ⩽ 360°. The metallicities for relatively short vertical distances (z < 2.5 kpc) show systematic fluctuations with Galactic longitude, similar to those of the thick-disc scaleheight, which may be interpreted as indicating a common origin, viz., the flare effect of the disc (Bilir et al., 2007, MNRAS). This suggestion is supported by the metallicity variations which we find as functions of radial distance. The metallicity variation at larger vertical distances (6.5 < z ⩽ 9.5 kpc) is small but monotonic. Three different vertical metallicity gradients could be detected: d[M/H]/dz = - 0.22(±0.03), d[M/H]/dz = -0.38(±0.06), and d[M/H]/dz = -0.08(±0.07) dex kpc-1 for the intervals z < 3, 3 ⩽ z < 5, and 5 ⩽ z < 10 kpc, respectively. Since our data cover the whole Galactic longitude interval, the resulting metallicity gradients can be interpreted as properties of the larger-scale Galaxy. The first gradient confirms the dissipational formation of the disc at short z-distances. The steeper gradient corresponds to the transition region between different population components of the Galaxy, and finally, the lowest value provides an adequate description of the inner-halo metallicity gradient.