The nearly free electron gas model is the standard introduction to explaining conduction in solids. In other words, no he didn’t invent it. Interestingly enough

The nearly free electron gas model is the standard introduction to explaining conduction in solids. In other words, no he didn’t invent it. Interestingly enough, the first model for explaining conduction was naively assumed to be a simple gas model. After quantum mechanics was introduced into the modeling, it was discovered that while not quite correct, it was not very far off either.