This paper presents a novel voxelisation tool designed for the electromagnetic simulation of metal composite materials, specifically in the context of 3D printed metal composite horn antennas. The tool addresses the limitations of traditional electromagnetic simulators, which struggle to accurately model hybrid structures composed of metal and dielectric components. The study employs two types of metal composite filaments, such as copper and brass-filled PLA, during the simulation of horn antennas across different fabrication stages: green, brown, and sintered. Through detailed material modelling and voxelisation techniques, the tool allows for realistic simulations that reflect the complex interactions of electromagnetic waves within these composite materials. Preliminary results indicate that while the green stage antennas exhibit poor radiative performance, significant improvements are anticipated post-debinding and sintering, suggesting a viable path forward for the development of efficient
metal composite antennas.