Metamaterials, arrays of subwavelength resonant building blocks, have been the focus of growing interest for both fundamental research and practical applications. These electromagnetic structures are very promising in developing low cost, ultrasensitive, and easy-to-use in room-temperature devices particularly for terahertz (THz) band to fully exploit wide-range potential applications of this scientifically rich spectrum. Beside atypical characteristics such as negative refraction, subwavelength imaging, and perfect absorption, metamaterials emulate some well-known quantum phenomena e.g. Fano resonance and electromagnetically induced transparency (EIT). This dissertation will cover design, fabrication, and characterization of perfect metamaterial absorbers and EIT metamaterials for THz sensing and communications. For sensing applications, a unique dynamic circuit model will be first presented to design and analyze metamaterial absorbers and to interpret their underlying absorption mechanism. Then inspired by stereoisomers in chemistry, a perfect stereometamaterial absorber will be introduced with interesting multifunctional characteristics that are controllable by polarization of the incident THz radiation. Subsequently, an electronically liquid crystal tunable perfect metamaterial absorber will be demonstrated. EIT metamaterials with slow light characteristics useful in ultrafast communications will be covered for communication applications. First, we will represent our unique approach to determine the effective thickness of EIT metamaterials as an open question in this area. Then a novel flexible EIT metamaterial will be presented with a tunable slow light response along with a model to interpret the operational principle of EIT metamaterials. Eventually, a novel platform will be introduced to design a Fano metamaterial thereby an EIT metamaterial is created with independent control of dark and bright states and with more flexibility in tuning its response as well as also interesting subwavelength focusing characteristic.