During the last decade, two-dimensional (2D) materials, exemplified by the well-known graphene that can be exfoliated from the bulk phase, have attracted intensive attention. The advent of novel 2D materials makes it possible to fabricate devices at the atomic scale. Here, I will briefly introduce three of the newly emerging 2D materials: silicene, borophene and Cu2Si. These materials contain only one atomic layer and have been successfully synthesized on metal substrates by molecular beam epitaxy (MBE). Scanning tunneling microscopy (STM) and angle resolved photoemission spectroscopy (ARPES) measurements have unraveled intriguing properties in these materials, such as the Dirac cones in silicene and borophene and Dirac nodal lines in Cu2Si. These novel properties are not only of fundamental interest but also essential for the future device applications.