In this paper we took into examination the use of chelation therapy for treating metal intoxication in humans. We divided this paper in four main parts: before all the principal causes of toxicity are exposed; second the chemical requirements (thermodynamic and kinetic), the interactions with the endogenous molecules and the target organs, as well as the biomedical restraints; as a third step the classes of chelators in use along with the specific treatments allowed are treated and as a final step the principal toxic metal ions are presented. Based on the presented material some conclusion are drawn on the state of art of metal chelation, and the basis are given for a rationale development of metal chelation, founded on chemical, biological and medical considerations.