My house has steel "2x4s" in the walls, can I hang cabinets, a TV, or some other heavy item from them?
Metal studs are great for framing walls. They are super light, easy to work with, straight. But you've discovered one drawback...they don't have nearly the strength of a wooden 2x4 for mounting things to it.
Metal studs do come in different gauges though. The heavier, the better.  But it sounds like yours are fairly lightweight.
Some options:

take down the sheetrock, add some wood 2x4s, re-sheetrock
find toggle bolts suited for this (they may exist, though I doubt any are rated for hanging actual cabinets or HD TVs).
add your own mounting panel on the outside...such as some nice finished furniture grade plywood. Since the plywood can be attached to multiple studs in multiple locations, it can spread the load.
get an entertainment system designed with its own 'wall' panel. Ikea has several, for instance: