A plastic closure is disclosed which is configured for enhanced performance and reduced closure weight. Notably, the closure includes a compound, internal helical thread formation including an upper retention portion which provides desired closure hoop strength and sealing performance, and a lower guide portion which is configured for light weight while functioning to guide the closure onto an associated container during application. The closure can further include a stepped top wall portion having a relatively thick outer region, and a relatively thin central region. A tamper-evident band of the closure can be configured to include a deformable free edge portion for enhanced tamper-resistance.