All firefighters agree that it's a pain to put out a fire in an electric car.

Yes. Lithium 🔥 peak temperature circa 2000c and steel’s melting point is under 1500c

Melt? Probably not likely. Weaken, maybe.

Depending on how much oxygen is available, lithium will burn veeery hot (>2000C) so when in contact with steel, it will easily melt it.