The invention relates to a method for closing already preformed and separated containers (19), for example trays, with a lid foil (24) in a closing station (3). The invention is characterized in that a deep-drawable foil is used as lid foil (24), that the lid foil (24) is deep-drawn in a forming means (23) of the packaging machine (1), and that the deep-drawing of the lid foil (24) is accomplished before the containers (19) are closed with the lid foil (24). The invention also relates to a packaging machine (1) suited for carrying out such a method.