Recent evidence supports the role of aggressive local treatment in the oligometastatic setting. In this review, we discuss the top 10 lessons we have learned from trials in oligometastatic cancers. Major lessons learned pertain to definitions of oligometastatic disease, outcomes, toxicity, costs, and the combination of ablative therapies with systemic therapy, including immunotherapy. Barriers to accrual for trials and upcoming phase III trials are also reviewed. These lessons may help to inform clinical practice and may be the basis for future research in the oligometastatic space.