Back in the day, aluminum Christmas trees were sold with color wheels and included literature warning you not to string lights on he tree. Fast forwarded to today, I have an old aluminum tree and am still warned by people not to put lights on it. I can understand that back in the day, lights burned hotter than deep fried hell and were nowhere as safe as modern day LEDs. Is there any reason to think that I could not safely light up my aluminum tree? I feel like a string of LEDs in good repair would not pose any real risk. Thoughts?
It isn't the heat that's the problem. The problem is the fact that those narrow strips of aluminum "needles" can work their way into a lamp socket (or the extension socket at the end) and make part or all of the tree "live" at some voltage that depends on exactly where along the string the contact occurs. AC-powered LEDs are just as dangerous in this regard as other kinds of lights.
At a minimum, ground the structure of the tree, and plug any lights into a good-quality GFCI. This should catch any single faults before they have a chance of becoming a double fault that could become a fire hazard.
Better still, just stick with the color wheel.