Intrinsic interstitial and antisite defects in GaN have been studied using density functional theory (DFT), and their configurations, electronic structures, and bonding properties have been characterized using the Wannier function. All N interstitial configurations eventually transform into N–N split interstitials, between which two π orbitals exist. The relaxation of a Ga antisite defect also leads to the formation of a N–N split configuration; however, its local Wannier orbitals are remarkably different from the N–N split interstitial. The different local Wannier orbitals around Ga interstitial configurations demonstrate that Ga interstitials are critical defects in GaN. The most striking feature is that Ga–Ga<1120> split interstitials can bridge the gap between nonbonded Ga atoms, thereby leading to a chain of four metallic-like-bonded Ga atoms along the <1120> direction in GaN, which may exhibit quantum properties.