Various emerging technologies, such as UM-MIMO, THz communications are under active discussion as promising technologies to support the extremely high access rate and superior network capacity in the future 6G mobile communication systems. However, such technologies are still facing many challenges for practical implementation. In particular, UM-MIMO and THz communication require an extremely large number of RF chains, and hence suffer from prohibitive hardware cost and complexity. In this article, we introduce the emerging paradigm called wireless communication enabled by programmable metasurfaces to address the above issues, by exploiting the powerful capability of metasurfaces in manipulating electromagnetic waves. We will first introduce the basic concept of programmable metasurfaces, followed by the promising paradigm shift in future wireless communication systems enabled by programmable metasurfaces. In particular, we give an overview of the two prospective paradigms of applying programmable metasurfaces in wireless transceivers, namely, RF chain-free transmitter and space-down-conversion receiver, which both have great potential to simplify the architecture and reduce the hardware cost of future wireless transceivers. Furthermore, we present the design architectures, preliminary experimental results and main advantages of these new paradigms and discuss their potential opportunities and challenges toward ultra-massive 6G communications with low hardware complexity, low cost, and high energy efficiency.