method for coating a static or moving metal substrate with a simple or complex shape, by means of an ultra-thin mineral/organic hybrid coating layer with a thickness comprised between 50 and 500nm, deposited on the substrate, characterized by the following steps: - a first aqueous solution comprising oxide nanoparticles is prepared, - an organic compound called a pre-polymer is prepared by polymerisation, resulting from the polycondensation reaction obtained by mixing a compound of a first category selected from the group consisting of a polyamine, a polyalcohol and a mixture of those, and a compound of a second category, selected from the group consisting of a polycarboxylic acid, a polycarboxylic anhydride, a polyepoxy, a polyisocyanate and any mixture of at least two of those; - the viscosity of the pre-polymer is measured in order to determine the state of progression of polymerization; - when the viscosity of the pre-polymer reaches a value comprised between 3000 and 25000 mPa.s (cP), the pre-polymer is dissolved in said first aqueous solution at a pH comprised between 9 and 13 in order to obtain a second aqueous solution; - the second aqueous solution is deposited on the substrate, which is found at a temperature below 50°C, the deposition being carried out on a metal strip on a continuous line by wringing the deposited solution on the faces of the strip by means of a set of wringer rollers, or the deposition being carried out on a metal strip on a continuous line by means of a system of coater rollers, or even the deposition being carried out on any metallurgical product other than strips by controlled spraying or dipping; - the coated solution is then dried with hot air, by induction or by infra-red radiations so that the total duration of deposition and drying is less than 10 seconds. - a first aqueous solution comprising oxide nanoparticles is prepared, - an organic compound called a pre-polymer is prepared by polymerisation, resulting from the polycondensation reaction obtained by mixing a compound of a first category selected from the group consisting of a polyamine, a polyalcohol and a mixture of those, and a compound of a second category, selected from the group consisting of a polycarboxylic acid, a polycarboxylic anhydride, a polyepoxy, a polyisocyanate and any mixture of at least two of those; - the viscosity of the pre-polymer is measured in order to determine the state of progression of polymerization; - when the viscosity of the pre-polymer reaches a value comprised between 3000 and 25000 mPa.s (cP), the pre-polymer is dissolved in said first aqueous solution at a pH comprised between 9 and 13 in order to obtain a second aqueous solution; - the second aqueous solution is deposited on the substrate, which is found at a temperature below 50°C, the deposition being carried out on a metal strip on a continuous line by wringing the deposited solution on the faces of the strip by means of a set of wringer rollers, or the deposition being carried out on a metal strip on a continuous line by means of a system of coater rollers, or even the deposition being carried out on any metallurgical product other than strips by controlled spraying or dipping; - the coated solution is then dried with hot air, by induction or by infra-red radiations so that the total duration of deposition and drying is less than 10 seconds.