You can also use a jigsaw fitted with a metal cutting blade to cut aluminium, and possibly some thin steels. Handy if you don't have an angle grinder but get fed up with the repetitive sawing motion of a hacksaw.

Off-topic, but looking at your avatar image, do you have any Roland instruments or connection to the Roland brand? Or are you just using it because it's the same as your name?
Just curious as I recognised the logo from my Roland drum kit and was wondering if you played an instrument.