(1) Background: The growing ubiquity of electromagnetic fields (EMF) due to rapid technological progress raises concerns about potential health implications. While laboratory experiments have generated inconclusive findings about adverse effects, EMFs have demonstrated efficacy in magnetotherapy. Earlier studies indicate that an EMF can trigger stress responses in organisms, the outcomes of which are dependent on the intensity of the EMF. (2) Methods: This study aims to explore the effects of extremely low-frequency EMF (50 Hz, 1 mT, or 7 mT) on metamorphosis and metabolism rates, which are indicators of stress, across different developmental stages of Tenebrio molitor, including adults, pupae, and larvae. (3) Results: Our findings reveal that exposure to EMF leads to accelerated weight loss, increased adult metabolism, and higher mortality; however, EMF exposure appears to have no impact on sugar levels or the rate and success of metamorphosis. Notably, significant changes were only observed under the influence of a strong EMF (7 mT), while the weaker EMF (1 mT) did not yield statistically significant outcomes. (4) Conclusion: The obtained results suggest that an extremely low-frequency EMF can be considered a stressor, with its effects contingent upon the specific parameters of exposure and the developmental stage of the experimental model.