While some may have actual metal work done to them a majority are repaired with very creative non metal fillers. I have a number of Cuban friends who have visited Cuba recently and have seen these vehicles in person or have relatives that own them. They use whatever they can obtain to accomplish repairs on damage, rust or rot and it isn't always metal or resin fillers we're accustomed to. The artisans who work on these vehicles are used to adapting what ever they can to keep these relics on the road.