Downhole well tool for permanently sealing a downhole well, wherein the downhole well tool comprises: - a housing having an upper housing section and a lower housing section; - a first compartment provided within the housing; characterized in that the downhole well tool comprises: - an expandable sealing element provided circumferentially outside the lower housing section, thereby forming a second compartment radially inside of the expandable sealing element and radially outside of the lower housing section; - a metal body provided within the first compartment; - a setting system comprising a heater for melting the metal body; - a fluid line providing fluid communication between the first compartment and the second compartment; wherein the well tool is configured to be in the following states: - a run state, in which the expandable sealing element is radially retracted; - an intermediate state, in which the metal body has been melted by the heater and is flowing from the first compartment to the second compartment; thereby expanding the expandable sealing element radially into contact with the well; - a set state, in which the melted metal from the metal body has been solidified within the second compartment. - a housing having an upper housing section and a lower housing section; - a first compartment provided within the housing; characterized in that the downhole well tool comprises: - an expandable sealing element provided circumferentially outside the lower housing section, thereby forming a second compartment radially inside of the expandable sealing element and radially outside of the lower housing section; - a metal body provided within the first compartment; - a setting system comprising a heater for melting the metal body; - a fluid line providing fluid communication between the first compartment and the second compartment; - an expandable sealing element provided circumferentially outside the lower housing section, thereby forming a second compartment radially inside of the expandable sealing element and radially outside of the lower housing section; - a metal body provided within the first compartment; - a setting system comprising a heater for melting the metal body; - a fluid line providing fluid communication between the first compartment and the second compartment; wherein the well tool is configured to be in the following states: - a run state, in which the expandable sealing element is radially retracted; - an intermediate state, in which the metal body has been melted by the heater and is flowing from the first compartment to the second compartment; thereby expanding the expandable sealing element radially into contact with the well; - a set state, in which the melted metal from the metal body has been solidified within the second compartment. - a run state, in which the expandable sealing element is radially retracted; - an intermediate state, in which the metal body has been melted by the heater and is flowing from the first compartment to the second compartment; thereby expanding the expandable sealing element radially into contact with the well; - a set state, in which the melted metal from the metal body has been solidified within the second compartment.