We follow the evolution of dressed coupled minibands as a function of an ac field intensity, nonperturbatively, for a wide field frequency range. High and low frequency limits are characterized by two different dynamic localization regimes, clearly separated by a breakdown region in a quasienergy map. Signatures of a metal-insulator-like transition by means of a field-induced suppression of a Peierls-like instability are identified. © 2000 The American Physical Society.