Hello again. I come with another physics concept I am struggling with. At first I thought I understood this but the more I think about it the more confused I get. Help! This post is with regard to the insulated 'Keep it Cool' boxes you can buy for taking on picnics or carrying cans of beer. I had always assumed that once you had put everything you want into the box you should then pack the spaces with something insulating to stop heat lose and movement by convection. However, a friend recently said to me that he puts metal things into his to keep the food cool because metal is a good conductor of heat and will therefore conduct the heat away from the food. This, to me, sounds physically sound. - shove a lump of cold metal in with the picnic and if any heat does 'get into' the box it will go to the metal instead of your food. Which theory is right and why?? Thanks.