This work introduces and investigates a metallic acoustic holographic lens to create an arbitrary acoustic pressure pattern in a target plane, using sound reflection phenomenon. The lens performs as a spatial sound modulator by introducing a relative phase shift to the reflected wavefront. The phase-shifting lens is designed using an iterative angular spectrum algorithm, and 3D-printed from powdered aluminum through direct metal laser melting. Then its capabilities to construct diffraction-limited complex pressure patterns and create multifocal areas are tested under water, numerically and experimentally. The proposed holographic lens design can drive immense improvements in applications involving medical ultrasound, ultrasonic energy transfer, and particle manipulation.