Heavy metals are naturally occurring elements with high atomic weight and density, widely distributed in the environment due to industrial, agricultural, medical, and technological uses. They are toxic and can cause health and environmental issues. Arsenic, cadmium, chromium, lead, and mercury are priority metals of public health significance due to their high toxicity. These metals are systemic toxicants that can cause multiple organ damage and are classified as human carcinogens. This review discusses their environmental occurrence, production, use, human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity. Arsenic is ubiquitous in the environment and exists in inorganic and organic forms. It is used in various industrial applications and can cause health effects through inhalation, ingestion, and skin contact. Chronic exposure to arsenic is linked to increased cancer risks, particularly in the bladder, kidney, skin, and liver. Arsenic toxicity is influenced by its oxidation state and solubility, and it can induce DNA damage, chromosomal aberrations, and oxidative stress. Arsenic trioxide has shown therapeutic value in treating acute promyelocytic leukemia. Cadmium is a heavy metal of environmental and occupational concern. It is found in sedimentary rocks and marine phosphates and is used in various industrial applications. Cadmium exposure can lead to pulmonary and gastrointestinal irritation, and chronic exposure is associated with decreased bone mineral density and osteoporosis. Cadmium is a weak mutagen but can cause DNA damage and oxidative stress. It is classified as a human carcinogen, with lung cancer being the most common effect. Chromium exists in various oxidation states, with hexavalent chromium (Cr(VI)) being the most toxic. It is used in industrial processes and can cause respiratory tract cancer and other health effects. Cr(VI) is a powerful oxidizing agent and can induce DNA damage, lipid peroxidation, and oxidative stress. It is classified as a human carcinogen, with lung cancer being the primary concern. Lead is a naturally occurring metal with many industrial applications. It is found in deteriorating household paints and can cause lead poisoning, particularly in children. Lead exposure can lead to neurological damage, reduced IQ, and developmental issues. Lead is a systemic toxicant that affects multiple organs, including the kidneys, liver, and central nervous system. It can cause oxidative stress and interfere with calcium-dependent processes in neurons. The molecular mechanisms of toxicity and carcinogenicity for these metals involve oxidative stress, DNA damage, and disruption of cellular processes. These metals can induce apoptosis, DNA fragmentation, and chromosomal abnormalities. The mechanisms of action vary among the metals, but they all contribute to health risks through their toxic and carcinogenic effects.Heavy metals are naturally occurring elements with high atomic weight and density, widely distributed in the environment due to industrial, agricultural, medical, and technological uses. They are toxic and can cause health and environmental issues. Arsenic, cadmium, chromium, lead, and mercury are priority metals of public health significance due to their high toxicity. These metals are systemic toxicants that can cause multiple organ damage and are classified as human carcinogens. This review discusses their environmental occurrence, production, use, human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity. Arsenic is ubiquitous in the environment and exists in inorganic and organic forms. It is used in various industrial applications and can cause health effects through inhalation, ingestion, and skin contact. Chronic exposure to arsenic is linked to increased cancer risks, particularly in the bladder, kidney, skin, and liver. Arsenic toxicity is influenced by its oxidation state and solubility, and it can induce DNA damage, chromosomal aberrations, and oxidative stress. Arsenic trioxide has shown therapeutic value in treating acute promyelocytic leukemia. Cadmium is a heavy metal of environmental and occupational concern. It is found in sedimentary rocks and marine phosphates and is used in various industrial applications. Cadmium exposure can lead to pulmonary and gastrointestinal irritation, and chronic exposure is associated with decreased bone mineral density and osteoporosis. Cadmium is a weak mutagen but can cause DNA damage and oxidative stress. It is classified as a human carcinogen, with lung cancer being the most common effect. Chromium exists in various oxidation states, with hexavalent chromium (Cr(VI)) being the most toxic. It is used in industrial processes and can cause respiratory tract cancer and other health effects. Cr(VI) is a powerful oxidizing agent and can induce DNA damage, lipid peroxidation, and oxidative stress. It is classified as a human carcinogen, with lung cancer being the primary concern. Lead is a naturally occurring metal with many industrial applications. It is found in deteriorating household paints and can cause lead poisoning, particularly in children. Lead exposure can lead to neurological damage, reduced IQ, and developmental issues. Lead is a systemic toxicant that affects multiple organs, including the kidneys, liver, and central nervous system. It can cause oxidative stress and interfere with calcium-dependent processes in neurons. The molecular mechanisms of toxicity and carcinogenicity for these metals involve oxidative stress, DNA damage, and disruption of cellular processes. These metals can induce apoptosis, DNA fragmentation, and chromosomal abnormalities. The mechanisms of action vary among the metals, but they all contribute to health risks through their toxic and carcinogenic effects.