There are some minerals that have important roles but only require trace amounts to perform their physiological roles.
Iodine: is needed in small amounts for its critically important role in the production of thyroxine (thyroid hormone responsible for basal metabolic rate). It is added to salt to prevent deficiencies. It is also found naturally in seafood.
Iron: is in the compounds of two proteins: hemoglobin and myoglobin. Hemoglobin carries oxygen in the blood stream. Myoglobin carries and stores oxygen in muscle. Iron is found in two forms in foods. Heme found in meat and non heme found in some vegetables. It can be challenging vegetarians and vegan to obtain adequate iron without supplementation.
Zinc: works the proteins in every organ. Trace amounts are needed to activate enzymes synthesis genetic proteins, wound healing and reproduction.
Selenium: helps to protect the body from oxidative destruction and activating thyroid hormone.
Fluoride: is not needed for metabolic function but is a desirable mineral for maintaining bone and tooth health. Replaces an hydroxyl ion in hydroxyapatite to make the more resistant fluorapatite.
Chromium: works with insulin to regulate the release of energy and blood glucose levels.
Copper: is needed to help form hemoglobin and collagen.