Knowledge of the fracture and fatigue behaviour of metallic alloys at extreme environmental temperature conditions is required to assess the safety of structural components operating in particular fields: aero-spatial, off-shore structures, power plants superconductors, polar Antarctic facilities, etc. Among the structural metallic alloys for civil, mechanical engineering and plant applications, steel S275 J2 is widely used, whereas aluminium alloys such as Al7075 T6 are significant especially for aero-spatial and polar Antarctic applications. In this paper, the main experimental mechanical characteristics of such metallic materials at room temperature as well as at low temperatures are examined. Three temperatures are considered: 293 K (+20 degrees C, room temperature RT), 243 K (-30 degrees C) and 193 K (-80 degrees C). The corresponding values of fracture toughness and endurance limit available in the literature are reported herein. Further, experimental tests have been performed to determine the unavailable mechanical properties. Then, the values of such fracture and fatigue parameters at various temperatures are critically discussed.