Just did a little test. My aluminum soda can didn't melt. It essentially combusted, the part over the flame.
I was using my 45 year-old Svea stove, which can heat like a blowtorch, the little part on the top that spreads the flame getting red hot. Within five minutes, the side of the can directly over the burner turned to what amounted to ash. I suppose you could melt it in a steel can but that wasn't what I was testing. But I also imagine you could easily boil water in a soda can with no problem, even without removing the top or anything. You'd have to watch what you were doing, just the same, because, you know, a watched pot will in fact boil. Besides, I don't know of anything thinner than a soda can except for foil, which is used in cooking all the time, including on campfires.
Probably the last think you'd try to be doing when cooking or in a "survival" situation would be trying to melt aluminum. And in my case, every single pot and pan in my accumulation of outdoor gear from my old Boy Scout cook kit on, is made of aluminum. And I even fixed breakfast this morning with an aluminum griddle.
I think there's a way to boil water in a birchbark container, provided you live where birch trees grow. It sounds like a lot of trouble, though.