So,
Im trying to mount my new lcd in the dead center of the family room. On the other side of the wall is the garage. i know that i have 2 waste take-away pvc pipes from the upstairs bath behind my mounting location.

when i use the stud finder it shows metal in the wall, a finishing nail stops dead after it passes thru the outer wall sheetrock and into what appears to be sheet metal?

Is it safe to drill thru this sheet metal and into the stud behind this?
I can only guess that the sheet metal enclosure is there to insulate the pipes from the garage and cold weather?
Anyone experience anything like this.
Home is in broomfield colorado, built 1992.

Thanks