Chelating resins operate similarly to ordinary ion-exchange resins.
Most chelating resins are polymers (copolymers to be precise) with reactive functional groups that chelate to metal ions. The variation in chelating resins arises from the nature of the chelating agents pendant from the polymer backbone. Dowex chelating resin A-1, also known as Chelex 100, is based on iminodiacetic acid in a styrene-divinylbenzene matrix. Dowex A-1 is available commercially and is widely used to determine general properties of chelating resins such as rate determining step and pH dependence, etc.  Dowex A-1 is produced from chloromethylated styrene-divinylbenzene copolymer via amination with aminodiacetic acid.
Poly metal chelating resin has almost negligible affinity to both alkali and alkaline earth metals; small quantities of resin can be utilized to concentrate trace metals in natural water systems or biological fluids, in which there are three or four orders of magnitude greater alkali and alkaline earth metal concentration than the trace metal concentrations.
Other functional groups bound to chelating resins are aminophosphonic acids, thiourea, and 2-picolylamine.