Could be a few things
1) quite correct, your pads may be down to the metal.
2) You may have something like grit stuck between pad and disc, moving it backwards might bring it out if that's the case.
3) Could be that pistons are sticking causing pads to make contact with the disc.
Anyway, with out have a good look, could be a number of things, if you have a centre stand, and a small jack, jack under engine until front wheel just off the ground, and spin it, see if you can find the noise.