Iron and aluminium are very common on Earth, but what makes them mineable is that at certain locations each metal is concentrated in sufficient quantities to make mining viable. The difference between a mineral deposit and an orebody is economics. A deposit containing 15 percent iron is uneconomic, but one containing 66 percent is potentially economic, depending on the quantities of any associated undesirable elements (gangue minerals) such as aluminium silicates and phosphorus.
One of the issues of smelting Fe and Al in Space is what minerals of each metal will be smelted. Different mineralogies dictate different smelting methods. Most open cut mines in Brazil and Australia produce an iron ore blended product of about 60 percent iron. Sweden mines iron ore from underground which contains 35 percent iron. This is because they are mining different iron minerals: mainly haematite rich ores in Brazil and Australia and predominantly magnetite in Sweden.
In Space, mineralogies may be discovered that are unknown on Earth.
The general process to get smelted metal is:
Mine minerals containing the metal
Concentrate the minerals required and remove as much of the gangue minerals as possible
Smelt the concentrated minerals to produce metal
Each step produces its own quantities of waste and product. If smelting is undertaken in Space, what is to be done with the waste products of smelting?
It is most likely that any concentrated forms of metals, available for smelting, will be found in clumps similar to the asteroids of our solar system or on planets or moons. For any space based smelter, transporting the raw materials will require a lot of effort, equipment and energy. Having a planet/moon based smelter for planet/moon minerals would be the most feasible option.
The other things to consider are why do you want to establish a Space based iron or aluminium smelter? What and where will its product be used? Will the smelter be operated on a continuous basis or a campaign basis during its production life and what will be the production life of the smelter? Do you expect the organization owing the smelter to operate it at a profit? Or will it be a government owned item of infrastructure that will be solely used for the advancement of science?
One issue specifically for smelting aluminium is that with our current Earth based smelting techniques a lot of electricity is required and it wasn't until electricity was produced on an industrial scale that aluminium became more widely available.
Maybe 3D printing could be an option for iron and aluminium as it is for titanium now: http://www.smh.com.au/technology/sci-tech/csiro-builds-sophie-a-dragon-20140110-30lpf.html