This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. 2 ||| 1556-6072/21©2021IEEE IEEE VEHICULAR TECHNOLOGY MAGAZINE | MONTH 2021 T he 6G era comes with the challenge of offering highly energy-efficient and autonomous communi- cations securely. In this direction, we report ener- gy efficiency (EE), energy harvesting (EH), and secure performance by employing power-collecting meta- surface-coated devices capable of supporting ultralow- power (ULP) transmissions. In contrast to what are called reconfigurable intelligent surfaces (RISs), where the reflect- ed signal can be combined at the receiver by being treat- ed as transmitted from a relay, the proposed metasurface claddings can be deployed at either the transmitter or receiver or at both. The passive metasurface-coated devices can achieve ultrahigh EE and EH in addition to signal detection, combined with an enhanced secrecy rate at the legitimate user or, if used from the other side of the link, spying capabilities of eavesdroppers under ULP transmission. To quantify their efficiency, we provide a holistic model for the utilization of the metasurface shells. Building upon this model, we present preliminary results that reveal the unprecedented superiority of the proposed concept compared to the RIS paradigm. Addi- tionally, we enumerate the main advantages of the new concept and define its role in the 6G era. Finally, possible research directions are discussed. Overview 5G mobile communication networks have already been rolled out in many countries and currently provide prom- ising services to billions of smart devices aimed at improving the lives of civilians. Nevertheless, the unprecedented increasing usage of smart devices driven by next-generation Internet of Things (IoT) applications will inevitably lead to an explosive growth of wireless data traffic. Apparently, the aforementioned growing demand of data-hungry 5G service has already overload- ed the existing cellular networks and appears to be a bad sign for new deployments [1]. Prior to the 5G release, the technology was focused on improving the performance of communication systems in terms of error rate, outage, and data throughput, assum- ing an unconfigurable propagation environment. As a con- sequence, the main focus of the wireless society has been to utilize complex and inevitably energy-hungry transmis- sion/reception as well as signal processing schemes ca- pable of mitigating the channel impairments by exploiting Digital Object Identifier 10.1109/MVT.2021.3119282 Date of current version: 16 November 2021 METASURFACE-COATED DEVICES A New Paradigm for Energy-Efficient and Secure 6G Communications Theodoros A. Tsiftsis, Constantinos Valagiannopoulos, Hongwu Liu, Alexandros-Apostolos A. Boulogeorgos, and Nikolaos I. Miridakis