Carefully scrape it off with a scalpel or sharp craft knife.
If your window is like my grand am the glue that holds the track and window together is not holding properly, so window keeps coming off track. I have not found a glue that holds yet.
take it to a glass shop, there is a special glue needed
I have the same problem on my 1998 Ford Expedition XLT. I have put it back on track about 5 times and keeps coming off again and again. I'm going to use the same glue the windshield installers used. I'm going to buy a tube of the glue from them, this will resolve the window from coming off track.
There is no metal that starts off as glue.
Depends on the kind of glue - "Name your glue"
Depends what kind of glue.
take it to a glass shop, it requires special glue.
you have to put more glue on it, it will glue itself to the old glue, and be easier to remove
Try Goof Off, it softens Super glue so you can pick it off.
It is a version of PVC glue.
Turn the glue gun on to loosen the glue, then, if the glue is persistent, use a wooden stick to CAREFULLY pick the glue off.
Depends on the type of glue, but most will come off with Goof -Off or Goo-Gone.