The Le-Matoran derived their principle of Faith from the virtues of Unity and Duty, the Onu-Matoran derived their principle of Prosperity from the virtues of Duty and Destiny, and the Ta-Matoran derived their principle of Courage from the virtue of Duty.
Almost every being in the Matoran Universe had a duty to serve.
- The duty of the Matoran of Metru Nui was to work their everyday jobs to the best of their ability.
- A Toa's duty was to defend the Matoran.
- Toa Hagah were given the duty to defend the Makuta the Brotherhood assigned to them.
- A Turaga's duty was to lead a Matoran village, or "Koro".
- The initial duty of the Brotherhood of Makuta was to create Rahi to populate the Matoran Universe.
- The Av-Matoran were, at one point, given the duty of preparing Karda Nui for Mata Nui's mission.
- It was the duty of the Bahrag to lead the Bohrok.
- The duty of the Bohrok was to cleanse the camouflage formed over Mata Nui's face.
- The duty of the Bohrok-Kal was to save the Bahrag in case they were trapped.
- Mata Nui's duty was to observe the galaxy, so he could be prepared to reform Spherus Magna stably.
- It was the duty of the Order of Mata Nui to carry out the will of Mata Nui.
- The Hand of Artakha, before disbanding, had the duty of keeping the Matoran safe.
- Tren Krom was created with the duty of overseeing the Matoran Universe while it was still under construction.
- The Barraki were initially created to keep order in the Matoran Universe, before becoming corrupt.
- It was the duty of Karzahni to repair Matoran that were sent to his realm.
- Sidorak and Roodaka had the duty of leading the Brotherhood of Makuta's Visorak horde.
- Hydraxon and the Maxilos Robots were given the duty of guarding the Pit and, if necessary, catching escaped prisoners.
- Axonn, Brutaka, Umbra, Vezon and Fenrakk/Kardas, Protodax, and Irnakk had the duty of serving as guardians for the Ignika on Voya Nui.
- The Chronicler had the duty of recording important events in the Matoran Universe.
- On the symbol of the Three Virtues, Duty was the spot on the left.