<p>Light rare earth elements are essential to the high-tech industry, with bastnaesite being a key mineral source for elements like cerium and lanthanum. Flotation is a critical process for securing a sustainable supply of these rare earth elements. Recent studies highlight the significant impact of metal ions on the efficiency of collectors used in bastnaesite flotation. This review focuses on the effects of metal ions on the performance of common bastnaesite collectors and systematically explores the fundamental surface chemistry involved. Despite their importance, there is limited research on how typical metal ions—such as iron, aluminum, magnesium, strontium, calcium, lead, and cobalt—affect widely used flotation reagents, including oleic acid, hydroxamic acid, and phosphate esters. Moreover, no adsorption models of metal ions on bastnaesite surfaces in open systems have been reported, and the mechanisms of metal ion-organic collector interactions in solution remain unclear. Addressing these gaps, this review identifies the need for better control of unavoidable metal ions and the design of metal-based flotation reagents to improve light rare earth flotation practices. The insights aim to offer practical guidance for the industry.</p> Graphical Abstract <p></p>