Nanoparticles synthesis has gained significant interest because of the unique characteristics and potential applications in numerous fields, including medicine, electronics, and environmental remediation. Top-down and Bottom-up are the two approaches of metal nanoparticles synthesis where Top-down method is the breakdown of bulk material and Bottom-up is building up of material from atoms. Top-down approaches including Mechanical milling, Laser ablation, Ion Sputtering, Thermal decomposition and Bottom-up approaches including Solid state methods, Liquid state synthesis methods, Gas-phase methods are the widely used methods. These conventional physical and chemical processes of nanoparticle synthesis are versatile and efficient but engages factors like high temperature and pressure, toxic reagents and production of hazardous byproducts. In contrast, green synthesis or biosynthesis of nanoparticles offers an eco-friendly alternative, leveraging natural materials and processes to produce nanoparticles with minimal environmental impact. The review explains the characteristics and application of several metal nanoparticles and their synthesis process along with advantages and disadvantages and focuses on the key advantages of green synthesis, emphasizing its contributions to sustainability, safety, and efficiency in nanoparticle production.