What kind of anger is he expressing? My boyfriend used to be extremely angry and always wanting to fight people who made him mad. He's totally different now, because of both maturity and (i'd like to think..)my disapproval of fighting. Try talking to him and getting to the root of his anger and discover new ways to manage anger/stress (working out, punching bags, etc)
My ex was a very angry person and he went on meds. It helped him to control it and feel happier. You could suggest that to him and, even beg, for him to look into it.
The other posters tell the absolute truth. There is NOTHING you can do to control it. I eventually had to leave my ex because of his anger and his complete disrespect for me, but your situation could be different. What got me through those times was reminding myself that I could only control myself. It sort of became my mantra and it made me stronger. I still try to use that to this day when things get crazy. He will behave however he choses. You can choose how you want to respond to it.