Like dark energy, dark matter is an extra, effective component needed to make our cosmological models fit well the data. Unlike dark energy however, dark matter is thought to be a ‘normal’ albeit unknown form of matter conceivable made of some unknown particles. Though not completely uncontested, evidence has been steadily accumulaing demonstrating that indeed this a tangible thing and not, for instance, an effective description of yet another failure of the general relativity, as dark energy indeed may well be.
Tangible it could be, however illusive certainly it is.
While its density is well-determined from cosmological observations, and results of its actions, galaxy structures and galaxies, can be seen with an (almost) naked eye, no convincing detection has been made so far. Indeed ever more powerful instruments and experiments keep only restricting the existing options without providing any definitive or at least plausible clues about its nature …
There is a number of plausible and considered models. However, as dark matter is one of those things nobody asked for, the current standard model of particle physics does provide a natural, or privileged given current state of knowledge, candidate … So the current searches for it have something from beating blindly around the bush …. However, in turn, this means that finding it will force us to revise this model. A quiet revolution in making …
While terrestrial experiments are constructed and conducted sqeezing the parameter space of different potential candidates with ever increasing efficiency … cosmological and astroparticle observations lead the way in providing complementary albeit circumstantial evidence … The next generation of efforts, SO, CMB-S4, DESI, LSST, Euclid, … is expected to bring plenty high precision constraints on diverse properties of the putative particles which constitute dark matter.