Wearable skin-contacting devices are extensively studied for their ability to provide convenient and safe health monitoring. A key aspect that controls their performance is the properties of the device electrodes. Optimizing electrode structure and materials can improve device functionality. This paper discusses the various properties required for optimal electrode performance, including mechanical, electrical, and biocompatible factors. To address these challenges, the paper considers altering electrode structures, developing flexible or soft conductive materials, and creating hybrid structures. Additionally, the integration of artificial intelligence is proposed as a promising direction to achieve smart devices. Wearable electronics has been developed to improve public health by enabling health monitoring and diagnosis. Skin-interfaced wearable electronics is a promising field due to its non-invasive and easily accessible nature. These devices can be categorized based on their functions, including sensing vital signs or biomarkers, and delivering stimuli to alert patients, both of which rely on electrodes. Therefore, it is essential to investigate and establish optimal electrode conditions to ensure the effectiveness of wearable skin devices. This paper first discusses the essential characteristics that the electrodes of wearable skin devices should possess, including mechanical properties related to skin elasticity, electrical properties related to device performance, and biocompatibility requirements associated with the skin-electrode interface. Due to the continuous changes in the shape of the skin caused by its high elasticity and low modulus, the electrodes need to exhibit high flexibility, adhesion, and the ability to conform to the shape of the skin. However, conventional skin electrodes made of rigid materials exhibit relatively higher modulus, making it challenging to meet these requirements. To address this limitation, various approaches for electrode structure have been developed, including the alteration of electrode structures, the development of new flexible and soft electrodes, and the creation of hybrid materials. The utilization of artificial intelligence and hybrid functionalities is recently proposed as a promising direction for the application of wearable skin devices. AI can be employed to facilitate real-time assessment of the user's physiological status by transmitting and analyzing biological signal data. Additionally, consolidating various functions of wearable skin devices into a unified system can establish an integrated hybrid system within a single device. The electrodes adopted in skin devices serve to interact with the skin and capture various electrical signals generated during this process. Moreover, they are utilized for stimulation purposes, including haptic feedback, electrical muscle stimulation, and neural stimulation. Depending on the type of the associated sensor or application, these electrodes can be designed in various forms. Specifically, the skin possesses various characteristics, and it is crucial to thoroughly consider these features when designing electrodes. One of the skin's most prominent features is its remarkable elasticity, allowing relatively unrestricted contraction and expansion, with the ability to stretch up to around 50%. The skin exhibits varying moduli across different regions, layers, or applied strain, with a wide range, from a few kPa to tens of MPa. Additionally, the skin secretes sweat containing various biomarkers which can also be a hindrance to adhesion. The skin alsoWearable skin-contacting devices are extensively studied for their ability to provide convenient and safe health monitoring. A key aspect that controls their performance is the properties of the device electrodes. Optimizing electrode structure and materials can improve device functionality. This paper discusses the various properties required for optimal electrode performance, including mechanical, electrical, and biocompatible factors. To address these challenges, the paper considers altering electrode structures, developing flexible or soft conductive materials, and creating hybrid structures. Additionally, the integration of artificial intelligence is proposed as a promising direction to achieve smart devices. Wearable electronics has been developed to improve public health by enabling health monitoring and diagnosis. Skin-interfaced wearable electronics is a promising field due to its non-invasive and easily accessible nature. These devices can be categorized based on their functions, including sensing vital signs or biomarkers, and delivering stimuli to alert patients, both of which rely on electrodes. Therefore, it is essential to investigate and establish optimal electrode conditions to ensure the effectiveness of wearable skin devices. This paper first discusses the essential characteristics that the electrodes of wearable skin devices should possess, including mechanical properties related to skin elasticity, electrical properties related to device performance, and biocompatibility requirements associated with the skin-electrode interface. Due to the continuous changes in the shape of the skin caused by its high elasticity and low modulus, the electrodes need to exhibit high flexibility, adhesion, and the ability to conform to the shape of the skin. However, conventional skin electrodes made of rigid materials exhibit relatively higher modulus, making it challenging to meet these requirements. To address this limitation, various approaches for electrode structure have been developed, including the alteration of electrode structures, the development of new flexible and soft electrodes, and the creation of hybrid materials. The utilization of artificial intelligence and hybrid functionalities is recently proposed as a promising direction for the application of wearable skin devices. AI can be employed to facilitate real-time assessment of the user's physiological status by transmitting and analyzing biological signal data. Additionally, consolidating various functions of wearable skin devices into a unified system can establish an integrated hybrid system within a single device. The electrodes adopted in skin devices serve to interact with the skin and capture various electrical signals generated during this process. Moreover, they are utilized for stimulation purposes, including haptic feedback, electrical muscle stimulation, and neural stimulation. Depending on the type of the associated sensor or application, these electrodes can be designed in various forms. Specifically, the skin possesses various characteristics, and it is crucial to thoroughly consider these features when designing electrodes. One of the skin's most prominent features is its remarkable elasticity, allowing relatively unrestricted contraction and expansion, with the ability to stretch up to around 50%. The skin exhibits varying moduli across different regions, layers, or applied strain, with a wide range, from a few kPa to tens of MPa. Additionally, the skin secretes sweat containing various biomarkers which can also be a hindrance to adhesion. The skin also