A noisy starter motor is not really a problem, its only if it fails to start or becomes difficult to start that is an issue. Is it making a metallic sound when turning the key before it starts? Or is it making the noise when it fires up?
The first could be the release on the starter not engaging properly, it will only get worse and eventually it will fail to start but if it starts its not a major issue for the moment. It can be cleaned or even refurbished
If its the second issue it could be the engine not getting enough oil on start up? Oil starvation is a big problem , but i doubt if this is the issue if you already think its related to the starter.