Why does a wall in my finished basement only have a steel plate and no studs?
As Legion600 suggested, you probably have steel studs as furring strips. You need to be sure you are not hitting protection plates installed on wood studs.



These protect electrical or plumbing lines close to the stud face, and you must never attempt to drill through these. Usually, if you drill several inches above or below such plates, you will hit wood. If you are hitting metal along the entire stud length, it is not a protection plate, but a metal stud. Metal studs in this application should be fairly light gauge and easy to drill through. Protection plates are about 16 GA and are not easy to drill through.

You may anchor objects to metal studs. They are sturdy enough when finish sheathing is attached along their length. Do not use toggles, the hole required is too large. It's best to use a number of self-drilling screws that are barely long enough to engage the stud face material after passing through the mount and wall finish. This avoids damaging any lines routed through the center holes of the stud. You can also use self tapping screws into pre-drilled holes, but drill very carefully so as not to damage any underlying lines when the drill breaks through the face material, and again, use appropriate length screws.