The fan runs loud whenever I use IMOVIE

A loud fan can happen if you have a large very high resolution project, like 4k, particularly if you have a low power CPU like i5. Or possibly you have some other high usage apps running at the same time.

Before doing anything else, try resetting your System Management Controller and the PRAM.

Resetting

the System Management Controller

Try resetting the System Management

Controller (but no longer available for the new M1 computers):

https://support.apple.com/en-us/HT201295

Resetting the NVRAM or PRAM

Try resetting the NVRAM or PRAM,

although this issue would be fairly rare:

https://support.apple.com/en-us/HT204063

-- Rich