Terahertz radiation refers to a broad electromagnetic spectrum range between microwave and infrared waves, which is also known as the terahertz gap due to inadequate materials and technologies for its generation and manipulation. Atomically thin two dimensional (2D) materials such as graphene, black phosphorus (BP) and transition metal dichalcogenides (TMDs) provide a powerful platform for manipulation of the propagation and detection of terahertz waves. Furthermore, hybrid metamaterials that feature the combination of artificially engineered metamaterials and 2D materials greatly facilitate the dynamic modulation or manipulation of THz radiation towards novel terahertz applications. Herein, we review recent progress in 2D materials in the terahertz domain and hybrid metamaterials with engineered functionalities through the incorporation of graphene, TMDs and BP. The emerging THz devices based on the modulation, nonlinearity, filtering, and plasmonics of 2D materials and metamaterials will be highlighted, and a brief discussion with perspectives and the remaining challenges will be concluded.