Metal is common in this game, but magnetite is not, so my idea of a magnet would technically most likely be an electric-powered iron block or something of that nature. What it would do is attract all drops in the area (range depending on electricity going into magnet) onto the metal block or whatever that is creating the electro-magnetic field. It can be nerfed to only attract metal drops or, if you fancy, to pull iron ores up from the ground. If the ores will be able to be pulled up, then I would strongly suggest that the magnets actually be used out of a new type of magnetite ore that is rare and may or may not be consumed in the process.
By the way, I loved the luminators lovely white light and microwaving effects in industrial craft 1, please get it back? =[