Abstract: An airtight metal melting furnace comprises a melting chamber enclosed by a lined metal shell and a refractory roof with a metal cover. An upper electrode and a hearth electrode are introduced into the melting chamber in order for a plasma or electric arc to be developed therein. Mounted above the roof cover is a slot table supporting means for measuring the temperature of the molten metal, means for drawing samples thereof, and means for introducing additives therein, the means being fixed in slots of said table. The cover and the furnace roof are formed with a channel which is shut by a gate. The slot table is mounted for plano-parallel movement, this permitting an alternate arrangement of said means above said channel and tight joining of the channel and the respective means.