VA loan is a fixed rate loan secured by the Department of Veteran Affairs. However, not everyone is eligible for this. Among those who can take advantage of this are those who have served the Armed Forces, Air Force, Marine Corps and the Coast Guard. They should have served for at least 90 days if they served during the wartime and at least 181 days if they served during the peacetime. The days should be continuous. Moreover, they should have not been dishonorably dismissed.
ARMs or adjustable rate mortgages are simply mortgages that have a varying interest rate in accordance with certain market conditions. You should also not expect your monthly payment to go down by much, if at all, even if interest rates go down. You also need to consider whether you are going to earn enough money to cover the payments if the they should go up.