Odd metallic chafing sound I bought a second hand road bike recently, I'm quite new to the field. 

I had a wet'ish ride and ever since getting a little bit of mud on my bike there's a metallic chaffing sound whenever I apply any sort of force to the pedals. I think it's coming from the chain but that doesn't seem to lack lubricant, is there a way to test this?
When applying a lot of force to the pedals I'll here more of a cringing sound from somewhere on the bike, I can't tell where that's coming from either :\
This could be coming from the bottom bracket, which will make noise when worn out and pedalling under load. One way to test this is to stand beside the bike, grab one crank in each hand and see if they can be rocked towards/away from the frame. There should be no play in this direction. This is described with pictures here.

If that's not the problem, then the following link has a rather comprehensive list of possible causes of bike noises.