Metal is a heat thief and will significantly affect the brew. You can go through a rigmarole of pre-heating but it will still drop in temperature much faster th

Metal is a heat thief and will significantly affect the brew. You can go through a rigmarole of pre-heating but it will still drop in temperature much faster than plastic. Handling metal at boiling temperatures is miserable. Burning yourself in your pre-coffee haze makes the ritual less enjoyable. Plastic is pretty damn good brewing material thanks to it's insulation. Metal and ceramics look great but you end up needing to add cladding and they are still inferior. Fortunately aeropress is forgiving compared to espresso so you might get away with the temperature changes but I would not be suprised by mixed results.