Bone scan for density vs. mets (need info)

I am scheduled for a bone scan this week to check for bone density. Is this the same scan that is done to look for mets? If so, is it necessary for me to ask those running the scan to look at the results for both, rather than at density alone. If it is not the same test, does anyone out there know what the difference is between the two?

Any information would be helpful. My scan is on Friday. Thanks as always for help.