Courtyard Villa Garage Wall
 

Attempting to put up shelves in the garage and hit some steel/metal.

The AC/Furnace system is in the closet behind the wall about six inches.

Any experience with this?

Take a look at where your duct work goes into the wall. If there isn't a duct in that area, then most likely you hit a stud.

Likely metal/steel studs (not wood). Get some strong drywall anchors. Flip toggles are recommended by pros.

I've got a CYV and have found that I have metal studs in the walls so more than likely that's what you have hit. I went to the store and bought different sizes of self-tapping screws for when I need to hang something from them. Other than that I just use wall anchors for in the drywall.

I just get the cheap stand up plastic shelf’s, you can cut the PVC tubing shorter or buy PVC tubing to make it bigger.

When hanging something on a wall, it is almost never necessary to drill into a metal or wood stud. Drywall anchors that expand behind the drywall and grip to it, and are spaced about 8 inches apart, will hold almost any weight you want to support, except possibly a large television.