Today, additive manufacturing (AM) has been wildly used for processing of metallic components with complex structure by vast alternations in microstructure and performances. Addition of rare earth elements (RE) is a potential route for improvement of the microstructure and properties in AM. Recent development of applications of RE in metal AM is reviewed in this article. With starting by a brief introduction of AM and basic understanding of the related microstructure, this review emphasizes on the fundamentals of the effects of RE on the melting pool and microstructure of the AM samples. Several key issues of application of RE in AM are also discussed. It is proposed that beyond of improvements of the microstructure and properties, limitation of the metallic system available for AM would also be expanded by RE addition and related processing parameter optimization.