A friend asked me if I could do some repair work to her truck. Seems the cab has some areas rusting out. I'd like to know, should use flux core or solid wire mig? And what settings would be good so I don't burn through? Having never done anything like this before. Going to do some practice before I do the job but not sure what gauge sheet metal I should get.
Any advice would be greatly appreciated.
Thanks

I would start with .o25 solid wire and something like 18ga or 20ga metal. Make a patch bigger than the rust area so you can weld to clean solid metal. I'd double check the settings on the inside of the machine but you'd probably be around 230ipm and like 17volts.

Using the smallest diameter wire will be the key to not burning thru the sheet metal.

Also watch this video and others on how to do it without warping stuff: