Many schools will require cover for their teachers, perhaps they’ll ill or on leave, and because of this supply teaching can be a job that’s always in demand, if you’re willing to travel far enough.
There are also other numerous advantages that come with supply teaching, also known as substitute teaching, and being able to teach a range of different subjects is one of them. One day you may find yourself teaching English, the next day Geography and then perhaps History.
You can then be teaching year 5’s one day and year 8’s the next (if you work in a middle school) and the range of experience you can gain is quite surreal. There’s also the benefit that you open yourself up to permanent teaching jobs if they become available and if you’ve proved to be a worthy supply teacher. This means that you’ll already be familiar with the school and their system rather than starting a permanent position in a school you’re unfamiliar with.