Materials Today Communications published an online review on October 31, systematically examining the application of machine learning (ML) in defect detection and classification for powder-based metal additive manufacturing, covering processes such as powder bed fusion (PBF-LB/M, PBF-EB/M), directed energy deposition (DED), and binder jetting (BJ). Methods include supervised, semi-supervised, and unsupervised learning, as well as CNNs, autoencoders, random forests, and GANs. Trend data: research papers in this field grew from 2 in 2015 to 234 in 2025; the review explicitly notes that ML evidence is mainly concentrated in PBF, while DED and BJ remain relatively sparse. Implications for powder AM industrialization: online quality closed-loop control is a key bottleneck for scaling production, and the review defines maturity differences in ML across processes, providing a roadmap for technology selection in monitoring, detection, and classification.