How can every substance be converted into a magnet (at room temperature)?
Not sure the context of your question, but fundamentally every electron, proton and neutron is a tiny magnet. Most substances do not show coordinated magnetic behavior of the electrons (the strongest magnets) at room temperature.
... but I suppose, if you got down to one molecule of a substance and made sure it had an odd number of electrons (the electron magnets tend to pair and cancel themselves out), you could in theory convert the substance into a magnet.
