This study addresses the seismic reinforcement of masonry structures with the use of metallic elements. There are various metallic elements, with several features that can be used taking into account their cost-effectiveness. Sometimes the application of metallic elements is expensive not only for its cost in itself, but also for the difficulty in implementation, which can increase costs. However, the use of metal elements allows for less intrusive interventions, which makes their use advisable when it is necessary to maintain the heritage value of buildings. Understanding the mechanisms of collapse of buildings when subjected to seismic activity determines the best method of seismic strengthening and also leads to an understanding of the functions of metallic elements in the reduction of seismic vulnerability. Even though each element is analysed separately, it is preferable to analyse the behaviour of the whole, seeing that it is the adequate performance of the building as a whole that is sought. In summary, this study presents several solutions to meet the basic modes of collapse of natural stone masonry structures using metallic elements when subject to seismic activity.