The expansion of mobile IoT (Internet of Things) devices has brought new urgency to securing ecosystems, and biometric authentication is increasingly central to this effort. Biometrics provides a uniquely robust mechanism for verifying identity, using human physical and behavioural characteristics that are non-transferable and convenient for users. This paper summarizes how biometric features are being used to strengthen authentication and access control in IoT contexts. We highlight emerging biometric technologies and their applications in mobile IoT devices. We also outline security challenges and recent solutions. The main objective is to provide an extensive overview of the latest developments and new patterns in biometric identification for IoT and to find out how these new ideas can help solve ongoing privacy and security issues.