What are the metalloids? When you are a student of science or engineering and you want to know what are the metalloids, you will need to learn what all the different types of metalloids are and what they are made of. You will find that there are many different types of metalloids and all the different types have their own characteristics as well as properties. Some of these metalloids include iron, tin, aluminum, magnesium, boron, phosphorus, silicon, mercury, ruthenium, bromine, sulfur and manganese all of which have different physical, chemical and electrical properties depending on what is in which they are mixed with other materials.