Metal complexation–based gelation imparts load-bearing hydrogels with striking properties like reversibility, self-healing, and mechanical tunability. Using a bio-inspired metal-catechol complex, these properties have been introduced to a variety of polymer hydrogels. We developed hyaluronic acid (HA) hydrogels by regulating the gelation kinetics of Fe³⁺ and a catechol cross-linker, including Fe³⁺-induced covalent bonding and coordination bonding. Dual roles of Fe³⁺ in catechol-modified HA (HA-CA), Fe³⁺-catechol coordination, and catechol oxidation followed by a coupling reaction, were selectively applied for different gelations. Tetra-poly(ethylene glycol) with catechol end groups (4-PCA) was also crosslinked through coordination bonds between catechol moieties and Fe(III) ions, which produce bis-complex and tris-complex depending on pH levels. The structure and properties of 4-PCA gels were examined upon the bonding types controlled by pH levels and molar ratios between catechol groups and Fe(III) ions. The results show structure and properties of gels can be controlled by geometries of crosslinking units as a strategy to develop novel polymer gels.