As you know, recently Appstore removed both MetaTrader 4 and MetaTrader 5 from their platform. This is very crucial point as most trader use their phone to trade and without these platform, they are forced to use Android or Windows to trade instead. Now with that in mind, there is a way to download through Appstore.
Firstly, go to AppStore and click the top right profile guy.
Next, scroll to the very bottom.
Click Sign Out
Now, find any of your friends who have installed MetaTrader 4 / MetaTrader 5 from their device and login with their Apple ID.
After login, click on "Purchased" and find MetaTrader 4 / MetaTrader 5
After finished downloading, make sure to sign out account and login back to your account. And there you have it! You have MetaTrader 4 / MetaTrader 5 in your IOS Devices.