Method and use of abandoning a well (2) or removing a well element (10) which is arranged in a well (2) by melting surrounding materials or by melting the well element (10), the method comprising the steps of; providing an amount of a heat generating mixture (6), the amount (6) being adapted to perform one of the desired operations, positioning the heat generating mixture (6) at a melting position in the well (2), igniting the heat generating mixture (6), thereby melting the surrounding materials in the well (2) or melting the well element (10).