This chapter explores the principles and innovations in using modified cyclodextrins for fluorescence sensing, focusing on their role in metal detection which find applications in environmental, analytical, and biomedical fields. Cyclodextrins improve sensor performance by forming host–guest complexes and nano assemblies, enhancing solubility, selectivity, and tunability. These structures, including polymer dots and micelles, are sensitive to factors like pH and exhibit unique properties when binding with various metals. Cyclodextrins combined with quantum dots also facilitate metal ion adsorption and fluorescence detection. The chapter offers a comprehensive overview of cyclodextrins' potential in fluorescence-based metal sensing.