Of course the metal can support a person. It's not like one side is floating in thin air. The way this is constructed, both sides of each step are supported and the metal seems thick enough to support quite a bit of weight.

The only thing that bothers me is that forward/backward motion of the steps would put a lot of strain on the connection to the wall or floor. With normal use, that motion is quite limited though.

I'm quite confident the designer of those stairs used the right thickness for the material used, which you can't judge from a picture.