<p>Metal additive manufacturing (AM), also known as metal three-dimensional (3D) printing, has emerged as a transformative technology with the potential to revolutionize the design and production of internal combustion engine (ICE) components. This review paper provides a comprehensive analysis of the current state-of-the-art in metal AM for ICE applications. It examines the various AM processes employed, including powder bed fusion (PBF) and directed energy deposition (DED), and their suitability for different engine parts. A wide range of materials, from aluminum alloys and titanium alloys to high-temperature superalloys and steels, are discussed in terms of their printability, mechanical properties, and high-temperature performance. The paper delves into specific applications, such as pistons, cylinder heads, exhaust manifolds, turbocharger components, and fuel injectors, highlighting the benefits of AM, including design freedom, lightweighting, improved performance, and part consolidation. Significant challenges, such as residual stresses, porosity, surface finish, and cost-effectiveness, are critically assessed. Finally, the paper explores future research directions, including the development of novel materials, process optimization, hybrid manufacturing approaches, the integration of artificial intelligence and digital twins, and the potential of AM for ICEs running on future fuels. The review concludes that while challenges remain, metal AM offers significant opportunities to enhance the efficiency, performance, and sustainability of internal combustion engines.</p>