Traditionally, trombones are made from brass, much like the other instruments in their namesake musical family. There are different types of brass achieved by mixing different percentages of copper and zinc, but those are always the primary two elements to achieve that type of metal.  Plastic trombones have become a popular alternative since the 2010s or so. They’re lighter than brass, and with an instrument that’s held straight out while you play, that can be a relief for players with arm or shoulder issues. Plastic is also cheaper and as such is touted as a great alternative for beginners and those who want to try out the instrument before committing fully to it. Plus, plastic trombones can be made in a variety of fun colors!