Interleukin (IL)-41 is a newly discovered and renamed cytokine or adipokine. IL-41 has also been called Metrnl, Cometin, Subfatin and Meteorin (metron)-like or Meteorin-β, and IL-39, respectively. IL-41/Metronl is a small secretory protein, which is widely expressed in vivo, especially in skin, mucosa and white adipose tissue. It plays an important role in neurodevelopment, white adipose browning, insulin sensitization, metabolism and inflammation-related diseases. The function and mechanism of IL-41/Metronl need to be further confirmed. This paper reviews the biological characteristics, expression, and role of IL-41/Metronl in metabolism and inflammation-related diseases, and provides new ideas for the research of therapeutic targets or drugs of related diseases.