Mechanical alloying (MA), super cooling process, etc. have been used to prepare amorphous phases, metastable solid solutions, nanocrystals, and so on. It is important to consolidate these powders for evaluating the physical properties, and for applications. On the other hand, shock compression can be used as an effective consolidation method for metastable material powders without recrystallization or decomposition. We had prepared metastable transition-metal system bulk alloys and compounds (Fe-Co, Fe-Cu, Fe-W, Co-Cu, Sm-Fe-N systems, etc) by using MA and shock compression. The Fe-Cu and Co-Cu metastable solid solutions showed a fit curve to the Slater-Pauling one. The Co-Cu metastable solid solution bulk alloy showed a magneto-resistance. The Fe-Co fine-grained bulk alloys show the higher coeicivity than that of molten alloy. In this paper, the preparation and magnetic properties of the metastable alloys (Fe-Co, Fe-Cu, Co-Cu systems) are reviewed, and the applications to materials science and engineering are discussed.