I think you should be prepared to remove all jewellery, all hair slides and grips, and anything else that has metal in it or on it, before you go through the walk-through metal detector. Some officers will insist you do that first, and some will wait for you to walk through and if you set the detector off then you'll have to take all your metal stuff off anyway.

I know I am going to set the thing off, so I take everything of except my rings as they are solid silver and clearly visible on a part of my body that could not disguise anything else.