We study the limiting angles of wetting of surfaces of low-carbon and stainless steels, copper, brass, aluminum alloys, and magnesium alloys by water, aliphatic alcohols, monocarboxylic acids, and some inhibitors. It is shown that the surfaces of metals with passive film are more hydrophobic than the surfaces of low-carbon steel, medium-carbon steel, and magnesium. The plasma electrolytic oxidation of aluminum and magnesium alloys enhances the hydrophilicity of their surfaces. The introduction of chromium to an oxide ceramic coating facilitates the hydrophobization of the surface. The mechanical pulse hardening of steel leads to the formation of a nanostructure of the surface, hydrophobizes it, and increases the adsorption of surface-active substances. Preliminary 2.5–15% plastic deformation increases the wettability of the surface by water, increasing the adsorption of organic inhibitors and somewhat decreasing the adsorption of inorganic inhibitors. The in-service degradation of pipe steel (30 years) decreases the wetting angles, the values of which are comparable with those for plastically deformed steel at 2.5% strain.