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Pull off the brackets for the wires there. Take a wire wheel and grind down one of those spots. If there isnt a hole tap on that metal with a screwdriver see if it breaks through. If it doesn't and you dont care about looks just paint that new fresh metal and let it go. If there is a hole and you want a proper repair thats a bit more work and will require welding.
Could also just choose to ignore it spray it all down with a self healing undercoat like Fluid Film or PFC just to slow it down. Will get you some more time but isnt really a "repair". Though like Tony said if its that rusty up there im scared to see the rockers, under-body, ex. That shell may not be worth a nice repair, but spraying it down to get a few more winters from it would be.