This is a fairly decent kit. Not the most accurate, but it looks like an M60 when completed. The T-142 tracks the kit comes with are OK, but not the greatest. The best and cheapest option is to replace them with the set from AFV Club. They are workable and look real good. They run about $10 or so.
The majority of the covering of the tracks is rubber. Just the center guides, end connectors and the track pin ends are metal. They tend to get a dark metal color. The rubber will look like an old truck tire.
BTW, the armor on the US M60A1 is not reactive, but passive. It is called applique armor. Reactive armor has an explosive charge inside to dissipate an explosive round. Passive armor is just extra stand off armor to detonate explosive rounds prior to them contacting the hull or turret.