I. Introduction  
A. Applications of IoT  
B. Importance of 6G and NextG Networks  
C. Era of Machine Learning  
D. A Primer on Graph Neural Networks  
E. Scope of the Article  
F. Survey Organization  

II. Graph Neural Networks  
A. Terminologies and Definition  
B. Architecture of Graph Neural Networks  
C. Types of Graph Neural Networks  

III. GNN for Internet of Things  

V. GNN for Networking  

VI. GNN for Tactical Systems  

VII. Opportunities and Roadmap Ahead  

VIII. Conclusion