The container used to melt metals is called a crucible.

https://en.m.wikipedia.org/wiki/Crucible

It is usually ceramic, which doesn’t really melt, and can get way hotter than most if not all molten metals without breaking. So they fill it with little pieces of metal, set it in the furnace, and wait for it to melt.

I used to think they were all more or less the same until I started buying my own and stopped using the ones they were giving away for free at college or the doctor's office. I am still grateful for the free condoms, but in hindsight, they weren't the nicest ones.

I would encourage you or anyone else using condoms to try different ones and see what you like. Be open minded and try the different sizes, thicknesses, and materials. For example, my favorite so far are the skyn elite, which is a non-latex. Neither me or my partner have a latex allergy, so it would have seemed unnecessary to use non-latex, but I just ended up liking them more.

I also second u/Trivial_specter 's advice, it's a good explanation.