(Minor correction, wizards have no access to heat metal. It's only available to druids, rangers, and bards. But at level 7 wizards have access to Conjure Minor Elementals, which can summon 4 magma mephits and they each have one daily casting of heat metal.)

Yep. While the bard-sorcerer maintains that level 4 heat metal, they can also do 2d10/turn with fire bolts if they don't want to expend additional spell slots. Also assuming that all of those hit, that's 110 additional damage beyond the 180 from the heat metal.