Technology of magnetism is kind of super sci-fi. Magnetism is one of the fundamental forces of the universe, like radiation or gravity. Anything that manipulates magnetism is playing with the stuff of the universe. That being said, it happens all the time in Sci Fi, and, as long as we’re allowing for the possibility of crazy sci-fi concepts like Superstrings, Probability Manipulation, Dark Matter, etc., magnetism ought to be considered in light of these other kinds of energies.
Take, for instance, a magnetic relationship that moves through one of the other dimensions described by superstring theory. A material might be super magnetic but only to another specific metal in the area. For instance, a gun might magnetize its bullets to a specific magnetic field in an alternative dimension, and then hit an enemy with that field, thus making the target a giant magnet for all further shots.
On the other hand, sometimes Sci-fi writers theorize exceptionally magnetic materials-alloys which are so respondent to magnetic fields that they might even fly by use of a planet’s magenetic fields. Obviously, these kinds of materials are highly speculative, but they are a favorite among UFO enthusiasts so I include the materials here.
A race that could make highly magnetic materials or that could channel magenetism through non-traditional dimensions would have mastery over atraction of the universe’s most abundant building material. It’s easy to imagine such a race using extraordinary powers of attraction to get large machines to put themselves together.