Abstract: A metal door construction has two sheet-metal panels 10,11 which form the flat sides of the door. The panels present folded side-edge portions 10a-10g, 11a-11e which extend parallel to and in contact with one another within a joint region 10f; 11e. One panel is provided with a double fold 10c, 10e which forms a pocket for receiving the straight end-edge part 11f of the other panel. The other panel is provided with an outwardly folded profiled part, in the form of a bead or like promontory 11b, on the other side of the joint region. The metal door may be provided with a mullion structure for cooperation with a similar metal door 3 to form a double door construction hung in the same frame. The mullion structure includes a plate 4 which covers a hooked latching bolt used to hold the two doors together and to prevent the door crack from increasing to a non-permitted extent in the event of fire.