i use a fisher I.D.Edge and found out by a friend who also used an edge that if you have a signal next to iron thats good the iron might null it out ,BUT if you set it to pick up some iron it will let you know that theres a good target
in the field the coil has as it will read as a positive/neg on the meter so becouse of the positive number you dig it (most of the time if it reads a low number say +3 or 4 its gold) and when you dig it you will get the junk in the same scoop so with the magnet in the scoop the junk iron/steel sticks to it so its easy to find so you might want to lower the dis.numbers to get some more gold in the scoop