Method for obtaining a component of a motor-vehicle structure by means of a hot pressing operation on at least one sheet element of light alloy, such as aluminium alloy or magnesium alloy, said method comprising the steps of: - providing a hybrid panel adjacent to a mould element having a forming surface, - wherein said hybrid panel comprises at least one sheet of plastic material in contact with at least one sheet element of light alloy substantially along the entire extension thereof, so that said hybrid panel has at least one layer of light alloy sheet and one layer of plastic material, - hot forming said hybrid panel in its entirety by pressing it against said forming surface of said mould element with a predetermined controlled pressure and by simultaneously applying heat, until the hybrid panel comprising said at least one sheet element of light alloy and said at least one sheet of plastic material assumes a configuration corresponding to that of said forming surface, wherein preliminarily to the hot forming step of the hybrid panel, the surface of said sheet element of light alloy which is to come in contact with the sheet of plastic material is subjected to a roughening treatment, so as to define surface asperities, wherein before said hot forming step said at least one sheet element of light alloy and said at least one sheet of plastic material are coupled with each other so as to be in contact substantially along their entire extension, in a loose condition, without any preliminary mutual connection, and wherein said at least one sheet element of light alloy and said at least one sheet of plastic material constituting the hybrid panel are caused to adhere to each other following softening by heat of the sheet of plastic material during said hot forming step, with the plastic material of the sheet of plastic material which enters into said asperities when it is softened by heat during said hot forming step, said method being characterized in that: - said first mould element defines a projecting forming surface, - the hybrid panel is clamped along its periphery within a vertically movable frame, - between the vertically movable frame and the hybrid panel clamped thereto a chamber is defined, - once the hybrid panel has been clamped within the vertically movable frame, gas under pressure is supplied within said chamber while frame 4 is lowered above the first mould element with the projecting forming surface until the hybrid panel is pressed in contact against the entire projecting surface, so as to be formed in the desired manner. - providing a hybrid panel adjacent to a mould element having a forming surface, - wherein said hybrid panel comprises at least one sheet of plastic material in contact with at least one sheet element of light alloy substantially along the entire extension thereof, so that said hybrid panel has at least one layer of light alloy sheet and one layer of plastic material, - hot forming said hybrid panel in its entirety by pressing it against said forming surface of said mould element with a predetermined controlled pressure and by simultaneously applying heat, until the hybrid panel comprising said at least one sheet element of light alloy and said at least one sheet of plastic material assumes a configuration corresponding to that of said forming surface, - said first mould element defines a projecting forming surface, - the hybrid panel is clamped along its periphery within a vertically movable frame, - between the vertically movable frame and the hybrid panel clamped thereto a chamber is defined, - once the hybrid panel has been clamped within the vertically movable frame, gas under pressure is supplied within said chamber while frame 4 is lowered above the first mould element with the projecting forming surface until the hybrid panel is pressed in contact against the entire projecting surface, so as to be formed in the desired manner.