Amortization Loans and Bullet Loans both have their advantages and disadvantages. If you plan to pay the loan back right a way, a Bullet Loan would be a good choice for you, however if you plan to pay the loan back over an extended time, an Amortization loan might suit you better.

Loans where the interest accrues over time and then the interest plus the principal are paid are known as "bullet" loans (derived from the theory that having to pay interest plus all of the principal at once is like taking a bullet by the borrower).

Rifle and bullet (The bullet is dependent on the rifle to accomplish its purpose)

None. A bullet is a bullet, regardless of what material it's made from.