The Smelter is an enemy that appears in Super Mario RPG: Legend of the Seven Stars. The Smelter is a member of the Smithy Gang and serves as the source for all of Smithy's creations throughout the game.
The Smelter itself in battle never attacks directly. Instead, it will produce liquid metal for Smithy who will then create Shypers to aid them in battle.
The Smelter is weak to thunder attacks meaning Mallow's Shocker will be effective in taking it out. The Smelter can be rather troublesome in battle as it will continue to produce liquid metal for Smithy to use. As such, the Smelter should be taken out first. A combination of Mario's Lazy Shell and Mallow's Shocker should be able to take it out in a few turns. Princess Toadstool should focus on keeping them healed.