This research article presents the characterization of the metacognitive strategies and socio-emotional experiences that primary school students activate when solving mathematical modeling tasks. A qualitative methodology was used, employing a multiple case study with an exploratory scope. Two work groups from 1st and 3rd grade were selected to closely observe the metacognitive strategies and experiences that children activate when solving tasks through collaborative group work. Video recordings were made while they solved the modeling tasks and were coded in Atlas.ti. For the analysis, category systems were used for metacognitive strategies and socio-emotional experiences, and these were cross-referenced with the phases of the modeling cycle. The analysis results show that 1st-grade children activated procedural strategies in the early stages of the modeling cycle, while 3rd-grade students used planning and monitoring strategies during the simplification, mathematization, and mathematical work phases. The most significant feelings of enjoyment, discouragement, and lack of control were generated during these phases. Both groups regulate their emotional reactions to persist in the task, controlling themselves to avoid distractions from the team. The regulation strategies were activated during the solution interpretation and model validation phases for both groups. In the 3rd-grade group, feelings of enjoyment and confusion emerged when they projected the model, detecting its strengths and limitations.