Sliding metal folding door with several vertical panels, always in pairs, and not wider than 850 mm in width. Welded tubular structure with an outer lining of vertical corrugated sheet metal and inner tubular reinforcement based on leaf height. Chain mechanism motorization, control box, latch key and photoelectric cell. Possibility of different outer and inner linings. The door can be made manual and close in just one direction, and it can incorporate a small gate within the leaf.