Zinc, as an essential metal, is necessary for the correct function of an organism. It is involved in biochemical processes that affect the immune response of an organism, and it acts as a neuromodulator in the excitatory synapses of the brain. Zinc is also applied in response to stressful stimuli. Zinc is an essential factor of gene expression and is important, at the cellular level, in maintaining the integrity of the cell walls. It influences organism ageing. Zinc is relatively abundant in nature, and it exists in a mineral form and rarely as a pure element. Zinc is used widely in industry and agriculture. In industry, it is utilized mainly in the processing of other metals as protection against corrosion. In agriculture, it is used in fertilizers and chemicals to produce pesticides. In certain areas affected by human activities, its concentrations increase, and large quantities of this metal can get into the food supply. In this paper, we focus on zinc metabolism and homeostasis, with an emphasis placed on the biological function of zinc. This study also deals with zinc deficiency and its effect on health. We also touch on the excessive intake of zinc and its toxicity.