You can sprinkle some baking soda on the rust and then scrub with steel wool.
Hi, here are 4 different ways you can try to remove the rust from your pans https://m.wikihow.com/Remove-Rust-from-Pots-and-Pans
I agree with Ann, once you've removed the rust be sure to season with pan with vegetable to prevent the rust from returning. :)
I use stainless steel scouring pads. NOT the steel wool. They rust on everything. A true stainless steel scrubber should last a REALLY long time. When you remove the rust dry with paper towels thoroughly then wipe down with cooking oil or olive oil.
Cast iron? It requires re-seasoning. Let us know, if so.
Or iron stains transfered from something else on to stainless? Then a scouting pad & Comet or Ajax.