Guitar fret wire is a metal strip installed along the fretboard that defines note positions and affects playability. Made from materials like nickel-silver or stainless steel, it comes in various sizes and shapes to suit different playing styles. Fret wire impacts tone, sustain, and comfort, with taller frets allowing easier bending and lower frets offering smoother movement. High-quality fret wire ensures durability, precise intonation, and a comfortable playing experience for both beginners and professionals.