Congress and the President?

I need to write a 5 page essay on the relationship between the president and Congress. How they help each other, hinder each other, what their relationship is like, etc. I have hit some main points, like they need each other to p laws and have a checks and balances system, but i still need 3 more pages of this. Can anybody give me more points I can hit in my introductory paragraph and then expand on them later to lengthen my essay? All inputs appreciated.... Thanks!