What kind of material can i use for a mold for molten metal?

You could research sand casting. That's the old school way.

First... this is science so, if you want specific answers, you need to ask specific questions.

Second... The melting point of aluminum is NOT 3600°F, it is 1220°F for pure Al.

Third... It is unlikely that you want to cast pure Al. A more common Al casting alloy is 360, Al-Si eutectic with a mp 1070°F but it really depends on what you will do with this casting.

Fourth... What shape do you want to cast? and how many castings do you want to make? The answer will be different if you want to make 2 castings vs 2 million castings. If you want a simple shape, a right circular cylinder or a rectangular block, you have many choices for permanent molds: steel, cast iron, graphite, copper, among others. If the shape is more complicated or if the dimensional requirements are tight, the mold design may be much more complicated. There are graduate level college courses on the design of castings. One consideration is how long do you want it to take to freeze. You should, at minimum, do the thermal analysis to be sure that the heat load (superheat and latent heat of solidification) can be absorbed by the mold so that the "equilibrium" temperature is below the solidification temperature of the alloy.

Regarding previous answers... If you wet the mold with water or any other volatile liquid immediately before pouring, it is very likely that the molten alloy will create a steam explosion and blow that molten metal right back in your face. If you plan to do this, please be considerate of others and do it by yourself so you are the only one injured by your stupidity.

A little knowledge is a dangerous thing and the most dangerous person is the one who does not know that he/she does not know. Consult your friendly neighborhood metallurgist or someone who has actual proven experience.

Edit (I delete my answer)

Gary said it all.

ps gary i have no intention of doing this because i have no idea what im doing thanks for the heads up though.

pss i was wondering about that water thing i kind of thought it might explode but everything ive seen about sand casting has included wet sand... ????

wet the sand and then allow it to dry in shape? this makes some sense...