Metamaterials (MTMs) are the artificially engineered materials possessing a number of exceptional electromagnetic properties such as negative values of permeability and permittivity, zero phase constant, backward wave propagation, etc. Due to their special features, they have widely been utilized in a number of microwave engineering applications such as the design of antennas, filters, and microwave integrated circuits. The most effective way of designing the MTMs is to use the left-handed and right-handed electromagnetic transmission lines. In this technique, the MTMs can be modeled as composite right/left-handed, epsilon-negative and mu-negative transmission line–based MTMs. The constituent circuit elements of the MTM transmission lines can be tuned together for tailoring the dispersion characteristics of the resulting MTMs. Such materials are popularly known as the dispersion-engineered MTMs. One of the unique features of dispersion-engineered MTMs is the excitation of zeroth-order resonance (ZOR) mode. At ZOR, the phase constant approaches to a zero value, and the guided wavelength through the MTM resonator becomes infinite. This phenomenon is widely known as the infinite wavelength mode of operation. In this mode, the MTM resonator under test works at an infinite wavelength, and its electrical footprint becomes independent of the frequency of operation. This leads to the potential for miniaturization of the microwave devices and components. In the modern era of tiny electronics, MTMs have extensively been utilized to design the compact devices that find applications in various industrial and commercial fields. The latest research in applied electromagnetics has expanded the scope of MTMs to the 2-D and 3-D metasurfaces, which are finding use in the advanced applications.