+1What you need is a small concentric coil and a metal detector with iron zone partly cut off.
Garrett ACE + 4,5" sniper coil
I'm new to metal detecting and Im having the same problem. I have a Garrett AT pro using pro zero mode can't get anywhere near a fence with it. What settings should I try?
I've never tried this but I read on another site that you can take a small coil(A Whites 4x6 in this example) and get near the fence/totlot iron structures, and ground balance much of the interference out. Lowering sens in tandom also makes sense. Manual, locked GB.