The article reviews the toxic mechanisms of five heavy metals—mercury, lead, chromium, cadmium, and arsenic—focusing on their acute and chronic effects on human health. These metals are prevalent due to industrial activities and can be absorbed through water, air, and food. The metals disrupt cellular processes, including growth, proliferation, differentiation, and repair, leading to a range of toxic effects. Key mechanisms include the generation of reactive oxygen species (ROS), weakening of antioxidant defenses, enzyme inactivation, and oxidative stress. Some metals selectively bind to specific macromolecules, such as lead with aminolevulinic acid dehydratase and ferrochelatase. Chromium, cadmium, and arsenic cause genomic instability and DNA damage, contributing to their carcinogenicity. Despite current knowledge, poisoning remains a significant issue, requiring preventive measures and effective treatments, such as chelation therapy. The review highlights the similarities and differences in the toxic mechanisms of these metals, emphasizing the need for better management of metal poisonings.The article reviews the toxic mechanisms of five heavy metals—mercury, lead, chromium, cadmium, and arsenic—focusing on their acute and chronic effects on human health. These metals are prevalent due to industrial activities and can be absorbed through water, air, and food. The metals disrupt cellular processes, including growth, proliferation, differentiation, and repair, leading to a range of toxic effects. Key mechanisms include the generation of reactive oxygen species (ROS), weakening of antioxidant defenses, enzyme inactivation, and oxidative stress. Some metals selectively bind to specific macromolecules, such as lead with aminolevulinic acid dehydratase and ferrochelatase. Chromium, cadmium, and arsenic cause genomic instability and DNA damage, contributing to their carcinogenicity. Despite current knowledge, poisoning remains a significant issue, requiring preventive measures and effective treatments, such as chelation therapy. The review highlights the similarities and differences in the toxic mechanisms of these metals, emphasizing the need for better management of metal poisonings.