To amplify the point(s) above, it is best to keep everything together rather than use the silly little plastic dishes for pocket change and such. I (and many others here) just stop before entering the security line and put EVERYTHING that might be a problem in the metal detector into my carry-on. I keep a small, outside pocket on the bag available for this. My keys, pocket change, pens, metal-banded watch - it all goes into that bag pocket. The only thing I keep out is my id and boarding pass in my shirt pocket. That way, at the metal detector, all I have to do is toss my carry-on bag, plastic liquids baggie and shoes on the conveyor belt and walk through.