Some transition metals (iron, copper, zinc, molybdenum,…) are essential nutrients for life. In plants they are involved in a plethora of processes, from photosynthesis to the immune response. In spite of their importance, there is a prevalent low metal bioavailability in most agricultural soils. This has a profound impact on crop production and human nutrition. Our research efforts are directed to understanding how plant metal homeostasis is modulated by and modulates plant-associated microorganism, with a particular emphasis in plant-pathogen interactions and in the legume-rhizobia partnership within root nodules. By studying these interactions, we also expect to unvell new processes controlling plant metal trafficking and specific metal allocation to key proteins.