If your cover already has Magsafe, it will hold super well. I'm waiting for the part where I can also load like this

Hello NunoR370
No, you don't need to attach a magnet to your mobile. Only the back of your mobile needs to be magnetic.
Some mobiles have a magnetic ring on the back (e.g. iPhone).
My mobile did not have a magnetic ring on the back. I bought a case with a magnetic holder (e.g. Sp Connect Phone Case).
Or you can stick a magnetic disc (thin metal disc).

Good evening Nuno, in my opinion this is the best phone holder there is: solid and modern. All you have to do is stick the magnetic ring on the back of your phone, which you'll receive with it, or order a case specially designed for all phone models.
Enjoy your evening!