O rion Nebula (Figure 1), also known as Messier 42 1 (or just M42, and also NGC 1976), is a diffuse nebula 2 situated in the Milky Way, roughly at 1,500 light years from us (planet Earth), being the closest region of massive star formation. According to data collected by astronomers the Nebula has a mass 2,000 times greater than the Sun and is 24 light-years across. The Orion Nebula is easily detected in the night sky with the naked eye (in an environment with low light pollution), being south of Orion’s Belt 3 . The Orion Nebula has been the most observed H II region due to 3 factors: its apparent size, low reddening and high emission measure. The main goal of this article is to give a chemical perspective of the M42. This cloud of gas is being heated by the intense radiation of the Trapezium stars 4 embedded within it. Figure 1 : Image taken by SAC (Section of Astronomy, Astrophysics and Aeronautics of Academic Section of Coimbra) 1- From the Messier catalogue;