These stars are hard to see, because they are not very bright and are quite small. They are however, very dense. It is the very massive stars which have spectacular violent endings. When an iron core forms in a massive star, the core collapses and triggers an explosion called a supernova. Betelguese is an enormous star.
Supernova explosions are the universe's form of urban renewal.
They create heavier elements than iron, such as gold.