Recently, phase change materials (PCMs) have attracted significant attention due to their promising applications in many fields like solar energy and chip cooling. However, the present PCMs seriously suffer inevitable leakage and low thermal conduction. Magnetism can produce invisible field effects in the surrounding space. If there exist magnetic particles within this region, the effects will act on them emerging various fascinating phenomena. Inspired by this, we introduce hard magnetic particles (which can keep the effect after removing the magnetic field) to PCMs synthesizing an unprecedented magnetically tightened form-stable PCMs (MTPCMs), achieving multifunctions of leakage-proof, dynamic assembly and morphological reconfiguration, superior high thermal (increasing of 1400%~1600%) and electrical (>104 S/m) conductivity, and prominent compressive strength. Novel free-standing temperature control and high-performance thermal and electric conversion systems based on MTPCMs are furthermore developed. This work is a significant step toward exploiting a smart PCM for electronics and low-temperature energy storage.