Feruchemy is an ability that allows you to store traits such as Health, Strength Speed, Weight, Memories etc. inside 'metalminds' as long as they are in contact with your skin. For example you can store your speed, but you will be slower while storing the speed depending on how much speed you are storing. You can draw on whatever traits you have stored. You are the only one who can use your own metalminds. You also know the exact proportions of all the allomantic elements.