The choice of a mute is something that varies according to the individual
If you want a metal mute, you should bear in mind that you will mix more "metal" in your sound set up
It is a relatively heavy mute, thus significantly reducing the amount of volume produced, by making the bridge heavier.
If you want to practice almost silently it's a very decent choice.
the only drawbacks, are that you have to be more careful than usual, so as not to damage the bridge of your violin, and that the sound really changes on some instruments besides getting just more quiet