Toilet flange that is PVC & Metal (metal is Rusted)

Please help, I need to get the PVC & metal part off to fix the flange and install a new one. The metal ring is completley rusted apart from the PVC, that is on the ouside of the pipe, no screws can hold down the toilet. The pipe is in a concrete slab. Sorry can't supply pic.

Rust will do nothing. Is it broken? Why do you want to remove it?

flange

Eacj installation is different. We would have to see yours to decide which would be the best way to repair or replace it.