The article reviews the mechanisms by which plants respond to heavy metal (HM) stress and their defense strategies against HM toxicity. Heavy metals, which are non-biodegradable and persistent in the environment, can accumulate in plants and cause significant harm to their growth and health. Plants have evolved various mechanisms to counteract HM toxicity, including the production of phytochelatins (PCs) and metallothioneins (MTs), which bind to and sequester metals at the intracellular and intercellular levels. Additionally, plants synthesize non-enzymatic compounds like proline (Pro) to enhance the antioxidant capacity of intracellular antioxidant enzymes. The article also discusses the role of arbuscular mycorrhizal (AM) fungi in HM detoxification by immobilizing metals and enhancing plant antioxidant defense systems. The review covers the effects of specific HM elements such as chromium (Cr), aluminum (Al), manganese (Mn), nickel (Ni), copper (Cu), and zinc (Zn) on plant growth and physiology, highlighting the diverse mechanisms by which these metals exert their toxic effects. Finally, the article explores the defense mechanisms employed by plants, including the production of PCs and MTs, and the role of Pro in stress management. The review emphasizes the importance of understanding these mechanisms for developing strategies to enhance plant resistance to HM stress and for phytoremediation efforts.The article reviews the mechanisms by which plants respond to heavy metal (HM) stress and their defense strategies against HM toxicity. Heavy metals, which are non-biodegradable and persistent in the environment, can accumulate in plants and cause significant harm to their growth and health. Plants have evolved various mechanisms to counteract HM toxicity, including the production of phytochelatins (PCs) and metallothioneins (MTs), which bind to and sequester metals at the intracellular and intercellular levels. Additionally, plants synthesize non-enzymatic compounds like proline (Pro) to enhance the antioxidant capacity of intracellular antioxidant enzymes. The article also discusses the role of arbuscular mycorrhizal (AM) fungi in HM detoxification by immobilizing metals and enhancing plant antioxidant defense systems. The review covers the effects of specific HM elements such as chromium (Cr), aluminum (Al), manganese (Mn), nickel (Ni), copper (Cu), and zinc (Zn) on plant growth and physiology, highlighting the diverse mechanisms by which these metals exert their toxic effects. Finally, the article explores the defense mechanisms employed by plants, including the production of PCs and MTs, and the role of Pro in stress management. The review emphasizes the importance of understanding these mechanisms for developing strategies to enhance plant resistance to HM stress and for phytoremediation efforts.