I have a column in my kitchen. As far as I can tell this is a decorative column, and doesn't contain anything structural — I live in a high rise, it really cannot contain anything structural.
Yet, according to my fancy stud detector, it has metal 4 inches from either side, as shown here:
This doesn't seem to be a corner bead — it seems to be an entirely different beast.
If you want to see the stud finder in action:
Can I drill through this? How thick is it? What is it? Can I still drill through this, and use a plastic toggle anchor?
UPDATE
So, there's a couple things in here. I bought a Depstech Boroscope (I do not recommend buying one of these, they suck, but then again, there's not really any decent competition for them). First, to answer people what the metal was — it was just boring studs.
Inside, it gets a lot more interesting, as you can see in the metal studs picture, there's some insulation. That's the hot water pipe. There's also a cold water pipe in there, and some electrical conduit. The column itself is pretty idiot-proofed, but there's no armor on the pipework, instead
Best Answer
The metal that you are detecting is probably the metal studs that are in each corner of the column. From the picture it looks like that column is also sheathed in drywall and so there may very well be a metal corner strip along each vertical edge as well. The metal studs width are typically going to be 3.5 inches. The drywall thickness from the adjoining sides is 0.5 inches and with the metal corner piece it adds up to the 4 inches that you are seeing.
As mentioned in comments this column is most likely a place where some part of the building infrastructure is located. It could be a structural beam, vertical routing space for water or gas piping or electrical wiring.
As to whether you can use conventional drywall anchors to mount light weight things to the living space side it would be best to be certain what is inside this thing before you go drilling holes in it. It could be OK but then again it could be something to be highly discouraged for a variety of reasons.