Method and device for monitoring a zone (2)of a metal structure (1) in terms of its electrical resistance in order to detect possible defects in the structure, by periodically passing current through the zone in different directions while measuring and recording voltage drops in a number of selected unit areas (a ij ) within the zone (2), and by combining, for each unit area (a ij ), at least two measured values recorded during at least two measurements made with current passing in different directions, and by comparing values obtained by at least one similarly obtained value made earlier.