I install 20 to 30 tv's a week and more and more of these installations are to homes with metal studs in the walls. If you are mounting a newer tv (even the larger ones are under 65 lbs) and your mounting a flat or tilt mount. there is no need for reinforcing the wall. You need to make sure your mount has a wall plate that is 24 inches or more so as to cover two studs. Find the center of the studs and use strap toggler bolts through 1/2 inch holes in the metal studs to secure the mount. On top of those 4 bolts I always suppliment the wall mount with an additional 4 strap toggler bolts spaced evenly to help keep the load spread. Remember you can torque down the toggler bolts that go through the metal studs but only tighten the supplimental ones to the point the washers dont spin.
Now for fully articulate mounts you MUST reinforce the wall. This is done by cutting 3/4 inch plywood (get the sanded type). Cut it to 30 inches by 24 inches and mount it to two metal studs. Use three toggler bolts for each stud. Before I mount it on the wall I cover the back with construction adhesive. It helps keep the plywood in place and helps distrubute the load of the tv around .
Once the board is installed you can use simple lag bolts to mount the TV mount to the wall. I've used this technique over 100 times. I am the number one rated installer in south florida. And I have never had a TV I have mounted ciome off the wall.
I will add that if your mounting to a rental property you brief the tenants that the glue will make the installation permanent and they should get approval from their landlord before you try this .