The potential of a system combining millimeter- wave (mmWave) communication and multiple- input multiple-output (MIMO) technology has motivated an extensive effort in both the research community and industry. With the much higher spectrum band, mmWave is considered to be a promising technology to solve the congestion problem in the sub-6 GHz band for future massive Internet of Things (IoT) systems. However, mmWave is still a long way from being a practical implementation for an IoT terminal due to high hardware cost and energy consumption. In this article, we introduce a new mmWave transmission technology called wireless beam modulation (WBM). The distinguishing feature of WBM is that bit information is transmitted through the propagation attenuation differences of signal beams instead of being carried by the original signal beam. While maintaining the high data transmission capability of mmWave frequencies, this change brings the advantage of high energy efficiency and low-cost mmWave hardware implementation to the IoT node. It can be deployed without shifter array and complex signal processing, such as precoding or even channel estimation. The basic idea of WBM is based on the recently proposed over-the-air modulation (OTAM) method but with several significant improvements. By formulating multiple beams at the access point (AP) node, WBM enables multiple- user access with spatial-division multiplexing, which significantly improves the spectrum efficiency compared to OTAM. Moreover, by aligning multiple beams between the IoT nodes and the central AP, WBM provides robust transmission and allows higher-order modulation. Hence, the proposed WBM achieves a good balance between high data transmission and spectrum efficiency with low hardware cost, which is promising for upcoming mmWave massive IoT systems.