Another plus is that you can simply forget about it once you've plopped the can of sweetened, condensed milk in a pan of boiling water.
Aside from the other excellent answers about the boiling point of condensed milk, even if you put pure water in a tin can and put that in boiling water, it would not.
Just boil that condensed milk right in the can and presto chango -- caramel!. In this recipe, sweetened condensed milk is cooked until it creates a deliciously rich milk fully submerged in a large pot (1″ above the can) and boiled for 3 hours. 1 can of sweetened condensed milk (regular or low fat).
It's very easy to make at home from a can of sweetened condensed milk! every half hour and be ready to add more boiling water as needed.
Boiling condensed milk in the can is the start of a great dessert.