GMR sensors and inductors used to detect metal / magnetic fields

Hello everyone, I have a question about metal detection and magnetic fields and such.

I know that inductors and GMR sensors can both be used to detect magnetic fields and/or metal objects, but I was wondering about the difference in usage between them. I think I have a pretty good understanding, but I was hoping someone could explain the difference between the two to me..

And inductor is affected by a magnetic field or when a conducting object enters into its own field, am I correct? How is this different from GMR sensor detection?

Thanks for any help!

--Steven