So, the decking that came with my trailer didn't come screwed to the trailer itself. My task today was to alleviate that problem in order to connect the floor framing to the trailer. These screws are what I used. They are called drill screws and maybe a couple of other things.
What they do is connect wood to metal, if you can see in the picture, there are little wings or tabs which bore out the wood and then the screw self drills into the metal once the tabs hit metal they shear off and finally that little notch visible in the image taps threads into the metal and tada wood secured to metal. These particular ones were about $6 for 15 screws, not cheap, but well worth it in the long run.