This paper focuses on the galling mechanisms occurring in stainless steels and aims to provide a better comprehension of the effects of microstructure on galling resistance. Five stainless steels are studied in this paper, namely Nitronic60, AISI660, 316L, 316LN (austenitic stainless steels) and Uranus45 N (duplex austenite-ferrite). Both surface topography and in-depth microstructure are characterized in order to determine the consequences of galling apparition. Experimental investigations at macroscopic and microscopic scales show that galling can occur following several mechanisms. Galling leads to either adhesive wear spots randomly distributed on the surface (tolerant galling), adhesive wear initiated on the periphery of the pin (moderate galling) or abrasive wear and smearing (severe galling). Depending on these categories, the galling threshold and severity are highly variable. Studying these specific mechanisms can help us predict and eventually increase galling resistance for a given material couple. Thus, several microstructural investigations have been performed in order to discuss about the possible origins of these galling categories.