Yes, you could use self-tapping fasteners, but I prefer drilling holes through the sheetrock and steel stud, then using Hilti 1/4-20 Togglers. Here's a link:
The problems I have with using self-tapping screws for mounting TVs on walls with sheetrock and steel studs are 1) it is easy to over-tighten (or under-tighten) and therefore not get a good solid hold and 2) since steel studs CAN flex you sometimes can't tell whether you've actually gotten the screw to tap the stud instead of pushing it away and 3) since you aren't drilling a hole you can't see if you've damaged audio/video/electrical lines inside the wall.
I use a good 1/2" drill bit or Unibit to drill a clean hole thru the rock and stud, and then insert the toggler. Proceed very cautiously and drill a small pilot hole first, if needed, to minimize risk of damaging audio/video/electrical/alarm/phone/plumbing/who knows what. Once you've finished the hole, you can look in it, or carefully put a finger or fish tape in it, and confirm that you've got a good area for a toggler and that nothing in the wall has been damaged. Also, make sure you have enough space inside the wall to insert the toggler and to tighten the screw all the way down.