Abstract <p>Various abiotic stressors universally affect the metabolic processes in plants, significantly limiting their growth and reducing their productivity. The stress factors include extreme temperatures, drought, salinity, UV radiation, and heavy metals. Plants, as organisms deprived of mobility, have developed complex and well-organized regulatory mechanisms to adapt to and resist abiotic stress conditions. In particular, the mechanisms utilize various biologically active compounds as tools to increase plant resistance to adverse environmental influences. The set includes primary metabolites (oligosaccharides, polysaccharides, their derivatives, polyols, amino acids, etc.) and secondary metabolites (terpenoids and phenolic compounds, such as flavonoids and phenolic acids). The compounds possess high antioxidant properties, suppress the accumulation and remove reactive oxygen species (ROS), and protect biological macromolecules (proteins, lipids, and nucleic acids) and cell structures from oxidative damage. The compounds play an active role in osmotic adaptation; chelate heavy metal ions to reduce their toxicity; and can function as primary signaling molecules to regulate the signals that control expression of many genes and enzymes involved in metabolic processes and associated with stress resistance. The biologically active compounds are important for adaptation and ensure the survival, stability, and competitiveness of plants in response to adverse environmental impacts.</p>