Thats behind the passenger wheel area. Severity? Fixable? Rust check sprayed on it already.
is it all the way through?
yes, cut out rusted metal, weld in new metal, grind it smooth and then paint it.
yes its all the way through
anyone know a good welder that can do it?
^^^^
Jason but you have to lick his rim to win 
just use bondo… (no one will know…)
except me… and i don’t plan on selling the car anytime soon
any good products that i can fill it with?
i was just kidding… never use bondo unless you absolutly HAVE to… its your frame rail too, so get it fixed by welding properly… that jason lange kid is a sick welder, talk to him nice, rub him bum like he asked, and buy him mcdonalds, and he might hook you up…
If your not into doing it the best way possible…grind out as much as you can and then try and goup on as much por15 as possible, on the inside of the rail as well…which will seal the rust off from oxygen…but an area like that is relatively simple to cut out and weld a patch in.