Dark matter interacts gravitationally with normal matter. If it exists and if it can be directed and controlled, it could be used to make stuff lighter or heavier. Big ifs. I'm not holding my breath.
Gravity is the weakest known force, orders of magnitued weaker than the other forces. Dark matter has never been measured on earth due to gravitational interactions. This is probably related to the fact that the particle responsable for the dark matter are spread out rather uniformly and not 'clumbed' together as ordinary matter. That normal matter clums together is caused by all the other forces, not by gravitation.
I doubt if dark matter can be used to make things lighter, possibly dark energy could be used for that (which is even more elusive than dark matter). It could only make thing heavier if there is a method to confine it. But because it seems that dark matter does not interact with normal matter (at least not often), I do not see how it can be confined to ordinary matter. Take notices that neutrinos also cannot used for this purpose, because the simply zap through us by the millions everyday, without us noticing anything. We have not found methods that to confine neutrinos yet. They seem to fly at speeds close to the light speed.
I doubt if dark matter can be used to make things lighter, possibly dark energy could be used for that (which is even more elusive than dark matter). It could only make thing heavier if there is a method to confine it. But because it seems that dark matter does not interact with normal matter (at least not often), I do not see how it can be confined to ordinary matter. Take notices that neutrinos also cannot used for this purpose, because the simply zap through us by the millions everyday, without us noticing anything. We have not found methods that to confine neutrinos yet. They seem to fly at speeds close to the light speed.