The evolution of massive galaxies is important for understanding key physical processes such as AGN feedback in galaxy formation and evolution. In a cosmological context, statistical properties of this population such as their abundance could also provide an interesting diagnostic test. There is mounting evidence that our knowledge of the galaxy stellar mass function at the high mass end is incomplete, and may even miss the dominant population of the very massive galaxies.
To achieve an unbiased census of massive galaxies particularly in the early Universe, it is imperative to account for the dust-obscured star-formation galaxies, which are most easily observed in the far-infrared and sub-millimetre. I will present our efforts and results in tracing this elusive population, their physical properties and triggering mechanisms, by employing a tripod approach of state-of-the-art galaxy surveys, cosmological simulations and artificial intelligence techniques. I will conclude by summarising our main conclusions so far, future outlook and also challenges therein.