A method for repairing defects in a substrate including the steps of placing a consumable filler slug in contact with the substrate in the vicinity of the defect; placing at least one electrically conductive cover sheet in contact with a portion of the consumable filler slug; bringing a first electrode and a second electrode in contact with the at least one cover sheet and applying a force; and transmitting electrical current between the electrodes, thereby resistively heating the at least one cover sheet and conductively heating the consumable slug and a portion of the substrate resulting in coalescence in a substantially liquid pool that fills the defect. The pool is then cooled to solidification under pressure. Alternative embodiments eliminate the need for the conductive cover sheet(s) by utilizing electrodes having increased electrical and thermal resistance. The consumable slug may be formed as a single unit or multiple sections, and may incorporate sacrificial retainers.