<p>The continuous extraction and utilisation of mineral resources have resulted in the release of significant quantities of heavy metal elements from ores into soil and aquatic ecosystems. Moreover, they were transferred and altered through the food chain, resulting in accumulation within the human body, which can readily cause irreversible harm. Humic acid (HA) is a macromolecular compound resulting from the decomposition of organic matter in nature, characterised by numerous active functional groups that offer extensive active sites for chemical reactions and have significant adsorption capacity for heavy metals. The intricate molecular configuration of HA renders the interaction process between HA and heavy metals quite complex. This work fully reviews the electrostatic interaction, redox effect, ion exchange reaction, surface complexation, and co-precipitation of humic acid with heavy metals. The interaction analysis of influencing factors between HA and heavy metals and its impact on flocculation was summarised. The potential for the resource utilisation of humic acid was ultimately examined. These may serve as excellent references for the application of HA in the treatment of heavy metal wastewater.</p>