Galaxies collide and merge over vast periods of time, leading to the formation of new stars and sometimes triggering the creation of supermassive black holes. When galaxies collide, their stars rarely collide because of the vast distances between them, but the interaction of their gas and dust can spark intense star formation. This process is called a starburst.
The Milky Way galaxy, for example, is on a collision course with the Andromeda galaxy, which will result in a galactic merger in about 4.5 billion years. This collision is expected to reshape the structure of both galaxies, but it will not be catastrophic for our solar system due to the vast distances between stars.