They say boys will become men when men are needed. I, however, feel this is too broad. Boys who have been shown how to be men will become men when men are needed. We cannot tell someone to travel to a designated place without giving them directions. In the same way, we cannot expect boys to become men without first showing them how to be men.
How do we do this? Through strong male role models (e.g. Fathers, Pastors, Older brothers), and immersing oneself in the Bible (The Bible is, quite literally, the ultimate guide to everything). How does the Bible help in this? Men - real men - have a strong sense of character and morals. In order to have a strong sense of character and morals, God must be present. Why? Because, without God, morality becomes relative. And when morality becomes relative, to quote the Bible, "[...] every man did that which was right in his own eyes." (Judges 17:6). Now because man is fallible, his sense of morals will be fallible as well (unless they come from God).
Real men do not come solely from strong male role models. Real men use the Bible as a guide; applications of it's teachings are an everyday occurrence. Therefore, real men, the men we wish our boys to be, use the role models to show them that it does in fact have an application in the real world (much like an algebraic word problem). Tracing them back to their roots, real men come from God, because real men base their beliefs off of His word.