Mike,
I'm new to both the SE and hunting in all metal, but here's what I've learned:
You will be amazed at the total # of signals that will register in all metal, particularly in a typical park or other area that has seen a lot of activity. The other posts gave good info on how to set up the detector in all metal mode.
In all metal, you will hear ALL metal! That's the part that will take some practice and getting used to. I mentioned this before in another post, but so far, its the best explanation I can think of to get you on the right track: you have to understand the difference between hearing and LISTENING. You will be HEARING everything...all the responses to metal targets. But you have to LISTEN for the desirable responses. With coins, it will be the higher pitched signals; for jewelry, medium range (there be pull tabs here too!). Iron usually gives low pitched tones. Try not to become too dependent on the meter readings, but know they are there to give more info on the target in question. Go by sound first, then, if you can separate or define a nice high pitch in the mix that is consistent or somewhat repeatable, check the meter and see where you stand. I usually use the iron mask set up, but then hit the detect button so that the smart-find screen comes up. You can then toggle between digital read out and the cursor screen.
Only practice will get you to the point where the background trash signals can be mentally ignored in favor of listening for good signals. Maybe you could find an area with relatively less trash to start with. I jumped in with both feet and hunted an old fairgrounds....sink or swim! It was pretty overwhelming. I finally found a deep old coin there in the middle of trash that pretty much reinforced that I was doing it right, but it will take more of those to get my ears really tuned in to hunting in all metal mode. I think it will be worth the effort in the end!
Knipper