It seems to be a common misconception that multiple port nics are little switches.. Not sure how we kill off this misconception but it really needs to die..
The other misconception is that bridging these interfaces turns them into switches.. The closest it would come to would be a hub, and a shitty one at that.. Bridging has some specific use cases where it makes sense to do so. Actual use case is when you change media type, say going to from a fiber connection to copper, or wifi to ethernet.
You can use multiple interfaces a lagg to loadbalance traffic through, again not optimal performance here.. If you need more than 1 gig for example you should use a 10ge interface ;)