Single negative metamaterials have been deliberated on in this chapter along with their properties and potential applications. Left-handed metamaterials, which have negative refractive indices and are used in microwave and optical range structures are rereviewed. This chapter demonstrates the presence of an acoustical metamaterial with a negative effective density and bulk modulus, demonstrating that it is an effective medium in the most precise sense. For those unfamiliar, negative-index materials (NIMs) are a subset of metamaterials distinguished by an effective negative index, which results in peculiar wave phenomena, such as reverse negative refraction. We examined how metamaterials respond to electromagnetic behavior, these are manufactured media are manufactured materials that differ from those of their components. We also have discussed the history of negative index materials, the primary design approaches, and some potential applications, such as sub-wavelength resonant cavities. Several real-world applications of microwave technology are also analyzed. The most promising possibilities for future metamaterials study are highlighted.