Aircraft wing assemblies having both composite and metal panels are disclosed. In one embodiment, a wing assembly includes a support structure, an upper panel assembly formed from a metal material and coupled to the support structure, and a lower panel assembly formed from a composite material and coupled to the support structure. The metal material may be aluminum, titanium, or any other suitable metal, and the composite material may be a carbon fiber reinforced plastic (CFRP) material or other suitable composite material. In another embodiment, the upper panel assembly includes a downwardly depending first web portion, and the lower panel assembly includes an upwardly depending second web portion, the second web portion being proximate the first web portion, and an interface member of an isolating material is disposed between the first and second web portions.