Are you sure you mean Melton wool?
Because Melton wool isn’t soft. It’s actually quite hard, stiff, rigid, tough, thick, dense – take your pick. It’s the fabric used for weatherproof overcoats and upholstery for its toughness and robust wearing characteristics.
It’s primarily a twill-woven fabric, which means it should drape and fold well. Then, it is fulled – pounded and agitated, causing the microscopic scales on individual wool fibres to attach to each other, resulting in a thicker, shrunken fabric*. Finally, the surface is napped – brushed to a fluffy, velvetty texture – and then shaved to remove these loose fibres.
I suppose one could say that Melton has a “soft” surface – like a low-pile corduroy, perhaps. But it is not what I would consider remotely comfortable or skin-kind. I certainly wouldn’t want to wear Melton next to my skin, like the handknit Blue-Faced Leicester wool sweater I’m currently wearing – and I absolutely wouldn’t consider it for underwear, as I would a fine merino or Wensleydale.
*: Felting achieves the same aim, but, technically, felt is made with fleece, whereas fulled fabrics are woven or knitted first.