The examples that Paul gives are pretty simple. Truth is like armor. Truth can overcome evil. Truth is stronger than any outward form of power. If you tell the truth, you never need to be afraid of anything else you've done or said.
Truth destroys evil.
Another kind of armor, is justice . The more you grow up, the more you grow spiritually, the more you become concerned with justice. It's not just playing fair. It's making sure that everybody has a place in the world. It's working to see that prejudice is always spoken out against.