For decades, numerous studies have been carried out to generate a mimetic model for the study of metastasis, the main reason for most cancer deaths, in order to elucidate the unknowns surrounding this pathology. To better understand this process of cell dissemination, more realistic models are needed that are able to faithfully recreate the tumor microenvironment (TME). Therefore, new tools known as tumor-on-a-chip and metastasis-on-a-chip have recently been proposed. These tools incorporate microfluidic systems and small culture chambers in which the TME can be accurately recreated thanks to 3D bioprinting. In this work, a literature review has been carried out on the different phases of metastasis, the different unknowns that remain for its complete understanding and the use of new models for the study of this disease. The aim is to provide an overview of the current panorama and the great potential of these tumor-on-a-chip systems for in vitro translational research into the molecular basis of this pathology. In addition, these models will allow progress towards personalized medicine by generating chips from patient samples that mimic the original tumor and the metastatic process in order to perform an accurate pharmacological screening and establish the most appropriate treatment protocol.