To give meaningful service. To prepare to receive the Melchizedek Priesthood and temple ordinances. To commit to, prepare for, and serve an honorable full-time mission. To prepare to become a worthy husband and father. Serving throughout the world is a great missionary force, going about doing good as did the Savior.
Missionaries teach truth.
They dispel darkness. They spread joy. They bring precious souls to Christ. On that special day when a mission call is received, parents, brothers and sisters, and grandparents gather around the prospective missionary and note his nervousness as he carefully opens the letter of call. There is a pause, and then he announces where the prophet of the Lord has assigned him to serve.