This review article explores the advancements in ultrasonic metamaterials (UMMs) and their applications in wireless energy transfer (WET) technology, particularly in ultrasound-driven piezoelectric and triboelectric nanogenerators (US-PENGs and US-TENGs). UMMs are engineered materials that can manipulate ultrasound waves, enhancing the efficiency and performance of ultrasound energy receivers. The article begins by introducing the fundamentals, classification, and design engineering of UMMs, followed by a detailed discussion on their recent progress in US-PENGs and US-TENGs. It highlights the innovative strategies and applications of UMMs in these devices, including their ability to improve mechanical and physical properties such as flexibility, stretchability, and sensitivity. The review also addresses the challenges and future perspectives of UMMs in US-ETs, emphasizing the potential for reliable integrated energy transfer systems through the transformation of metamaterials into active mediums for generators. The article concludes with a comprehensive overview of the latest advancements and practical applications of US-ET technology, highlighting the unique advantages and limitations compared to other WET technologies.This review article explores the advancements in ultrasonic metamaterials (UMMs) and their applications in wireless energy transfer (WET) technology, particularly in ultrasound-driven piezoelectric and triboelectric nanogenerators (US-PENGs and US-TENGs). UMMs are engineered materials that can manipulate ultrasound waves, enhancing the efficiency and performance of ultrasound energy receivers. The article begins by introducing the fundamentals, classification, and design engineering of UMMs, followed by a detailed discussion on their recent progress in US-PENGs and US-TENGs. It highlights the innovative strategies and applications of UMMs in these devices, including their ability to improve mechanical and physical properties such as flexibility, stretchability, and sensitivity. The review also addresses the challenges and future perspectives of UMMs in US-ETs, emphasizing the potential for reliable integrated energy transfer systems through the transformation of metamaterials into active mediums for generators. The article concludes with a comprehensive overview of the latest advancements and practical applications of US-ET technology, highlighting the unique advantages and limitations compared to other WET technologies.