Although, NPs have potential to improved plant resistance against abiotic stress, increased nutrient usage efficiency, and sustenance of agricultural production. However, reactions of NPs in soil matrices, particularly their movement, perseverance, and biogeochemical reactions in soil–plant system under heavy metals (HMs) were not well understood. Therefore, this review presents the latest research in order to clarify the molecular interactions, beneficial transformations, and detoxification processes of NPs in plants and evaluates their roles in these processes. It further aims to quantify the benefits and risks, and give future directions for NPs design and applications in environmental remediation and agriculture. NPs significantly enhanced agricultural outcomes through mechanisms such as regulating HMs uptake, boosting antioxidant enzyme activity (up to a 60% increase), altering soil properties, and optimizing physiological metabolism. NPs amendments raised crop output by 20–55% while reducing disease and nutrient leaching to 50% and 30%, respectively, and improving the soil’s carbon sink by 15%. Meanwhile, green-synthesized nanomaterials offer eco-friendly alternatives in remediation through processes like adsorption, oxidation, coprecipitation, ion-exchange, photocatalysis, and nanophytoremediation, achieving 100% pollutant removal efficiency for elements like hexavalent chromium using iron NPs. However, challenges such as NPs accumulation in food chains, potential toxicity to non-target species, and physiological disruptions necessitate solutions like microbiome co-delivery and stimuli-responsive systems to balance safety and effectiveness. In order to increase the available resources and address the worldwide food safety issue, the use of NPs in agroecosystems might be a crucial step towards sustainable farming. Therefore, the influence of NPs on soil, and plant antioxidant defense systems and oxidative stress activation under HMs should be studied using molecular, physiological, and biochemical techniques. For this purpose, real-time polymerase chain reaction (RT-PCR) analysis, illumina MiSeq sequencing, pyrosequencing analysis, metagenomics, metabolomics, proteomics, and functional assays etc. could be most useful for NPs risk/benefit evaluation.