Power supply transformer shielding question

[Morocotopo]

Hi fellow DIYers, I have a question (yes, another one!):
If I make a power supply for my pedalboard, to be placed at one corner of it, right next to the pedals, will using a grounded metallic box for it (versus a plastic one) avoid the transformer´s electromagnetic field to get to the outside of the box and induce hum in my audio cables/pedals/patch cables/etc?

thanks for reading

Morocotopo