Melatonin is an strong anti-oxidant, anti-inflammatory, anti-viral, immune modulator and helps with calming cytokines, controlling ROS, boosting innate immune function and providing a mild sedative effect. It is made by the pineal gland, the gut and all mitochondria (when in darkness). People make less as they age but can easily supplement. Typical dosing is 1-10 mg. Supplementing melatonin encourages production of ATP and in turn more melatonin.
Melatonin Biochemistry by Dr. Been Medical Lectures - explains how it is part of COVID MATH protocol in home and hospital care