I would just like to know as I like to download a lot of them and I am scared my computer could be infected
Thanks
An mp4 file isn't an executable, so it will not run any malicious code directly. Therefore, if a mp4 file contains malware that wants to execute instructions, it has to exploit a vulnerability in the program that plays the file. This can either be a known vulnerability that hasn't been patched or a 0-day.
So, you can download mp4 files without any hesitations.
If you suspect any mp4 file to be suspicious, you can visit https://www.virustotal.com/gui/home/upload and scan the particular file with different antimalware vendors at the same time.
Regards