I just got my first pair of clipless pedals and shoes yesterday. The shoes came with some metal spikes that can be screwed into the toe. What is the purpose of these spikes and do I need to put them on.

they are for climbing really nasty condition hills on foot and you do not need to put them on unless you anticipate bad conditions

Yeah, they are called toe spikes. You don't need to put them in, but I have them in my shoes and there is a signifigant amount of added grip when they are in there. However, I have to push my bike up usually semi-soft dirt that allow the spikes to really dig in. On other surfaces such as more desert oriented they might not be as useful (just guessing, never tried them in other conditions).