Plays a crucial role in the formation of lipid droplets (LDs) which are storage organelles at the center of lipid and energy homeostasis (PubMed:19278620, PubMed:21533227, PubMed:30293840, PubMed:31708432). In association with LDAF1, defines the sites of LD formation in the ER (PubMed:31708432). Also required for growth and maturation of small nascent LDs into larger mature LDs (PubMed:27564575). Mediates the formation and/or stabilization of endoplasmic reticulum-lipid droplets (ER-LD) contacts, facilitating protein and lipid delivery from the ER into growing LDs (PubMed:27879284, PubMed:31178403). Regulates the maturation of ZFYVE1-positive nascent LDs and the function of the RAB18-ZFYVE1 complex in mediating the formation of ER-LD contacts (PubMed:30970241). Binds anionic phospholipids including phosphatidic acid (PubMed:30293840). Plays an important role in the differentiation and development of adipocytes (By similarity).