A method of preparing a substrate to receive a metal coating deposited by thermal spraying, the method including the following steps: a) depositing a layer of adhesive on the zone to be coated, the layer having a uniform thickness greater than 10 μm and less than 100 μm; b) before the adhesive dries, cold spraying a metal powder onto the zone to be coated, so that powder particles become embedded at least in part in the layer of adhesive; and c) drying the adhesive in which the powder particles remain held captive, thereby forming an undercoat suitable for receiving a metal coating deposited by thermal spraying. The method is applicable to protecting the leading edges of fan blades.