METLIN in general is a very popular database and set of tools for HPLC, but METLIN small molecule retention time (SMRT) dataset has a special place within this framework. It is one of the most often used dataset in high-performance liquid chromatography (HPLC) for training models aimed at predicting retention times in both reverse phase (RP) and hydrophilic interaction chromatography (HILIC). Unlike gas chromatography, where the biggest and most commonly used dataset is commercial (i.e., NIST retention index database), METLIN SMRT is publicly available, which boosts its applicability and popularity even more.