Metrics?

This is an request for some information for a presentation I'm looking at putting together. I was wondering what special things that people out there use routing metrics for? For example, IGP metrics might be used to determine the shortest path through a network when two paths exist. Some people define these staticaly, some dynamicaly. Metrics in the EGP might be used to tell a peer or customer the "distance" from the destination from that particular edge location in your network. Obviously, these are the simple uses, what are the other uses that folks put metrics to? -Chris