Platinum Group Metals — platinum, palladium, and rhodium — are the rare precious metals found inside catalytic converters. These metals act as catalysts that convert harmful exhaust gases (carbon monoxide, hydrocarbons, nitrogen oxides) into less harmful emissions. PGMs are extracted by specialist refiners who crush the ceramic substrate and recover the metals through a chemical process. Rhodium is the most valuable of the three, followed by palladium and then platinum, though market prices fluctuate. In the New Zealand scrap trade, PGMs are the reason catalytic converters can be worth anywhere from $20 to over $400 depending on type and condition.