The only thing you should consider when using a multimeter is that the aluminium frame is not a good conductor because of the surface oxide which builds up immediately after cutting through the material. The oxide layer has very high resistance, which can fool the meter, but if you scratch the surface, or wet it a little, it will show low resistance. This is normal, so if the frame is connected to the earth and you want to measure just to be sure, then you must be aware of this.