Essential micronutrients are minerals and vitamins that are crucial in human growth, development, disease prevention, and well-being. The human body cannot synthesize them; they must come from diets. Although various sources, such as fruits, vegetables, eggs, meats, and seafood, are rich in some essential micronutrients, most people live on a diet based on staple crops, such as rice, corn, wheat, millet, cassava, and potatoes. These crops contain low levels of essential micronutrients. An insufficient intake of them can cause either malnutrition or hidden hunger, leading to detrimental effects on human health. It is estimated that about two billion people worldwide suffer from deficiencies of essential micronutrients, which signifies a serious public health concern worldwide. Biofortification of staple crops, such as conventional breeding and agronomic approaches, has made progress in increasing the contents of essential micronutrients, but such methods are relatively less effective. Metabolic engineering is another strategy for enhancing essential micronutrients. This chapter is intended to briefly introduce priority essential micronutrients, their roles and recommended dietary allowance, and conventional breeding efforts made to improve their contents in major staple crops. Emphasis is placed on metabolic engineering of priority essential micronutrients, approaches for their engineering, and current progress. The United Nations Sustainable Development Goal 2 (UN-SDG2) has set forth a goal to end all forms of hunger by 2030. Metabolic engineering should make a significant contribution to the UN-SDG2 goal.