I probably looked over something and will sound like an idiot, but I just read that in space, if two pieces of uncoated metal touch they are fused together. Protoforms could be some sort of organic layer of armor that's weaker than raw metal. It is durable enough to get through space, but rather ineffective in battle. Cybertronians themselves are probably not metal, but their armor is. In 2007, Megatron had some sort of custom armor that was strong and able to go in space. Maybe he had a special coating to keep it safe. So what do you think, plausible? Are there any huge flaws I am overlooking?