Abstract: Wood was widely used in outdoor buildings and engineering structures due to its renewability, sustainability, and excellent mechanical properties. However, it was highly susceptible to biological degradation, and preservative treatment is therefore required to improve its durability. With the restriction of chromated copper arsenate (CCA), copper-based preservatives represented by alkaline copper quaternary (ACQ) and copper azole (CuAz/CA) had been extensively adopted. Nevertheless, the release of active copper ions from these systems significantly altered the interfacial electrochemical environment and accelerates the corrosion of metal fasteners, which had become a critical issue affecting the durability of timber structures. This paper systematically reviews recent advances in the corrosion of metals in preservative-treated wood, with emphasis on copper release, galvanic corrosion mechanisms, and the regulatory effects of moisture, oxygen, and the wood chemical environment on corrosion behavior. The corrosion resistance of different metallic materials is also compared. Previous studies have shown that the corrosion rates of metal fasteners in ACQ- and CA-treated wood are generally higher than those in CCA-treated wood, with corrosion being further accelerated under high-humidity and saline conditions. In addition, the local pH of wood can decrease to 4–6, thereby promoting copper release and localized corrosion. Compared with carbon steel, galvanized steel, and aluminum alloys, stainless steel exhibits the highest corrosion resistance. Common corrosion testing methods and engineering protection strategies are also reviewed. Furthermore, current limitations in understanding the coupled corrosion mechanisms and service-life prediction are discussed. This review aims to provide a theoretical basis and technical reference for the durability design of preservative-treated timber structures and the corrosion protection of metal fasteners.