A thermite torch is disclosed that contains a thermite composition made of a bimodal mixture of nano-sized particles and micro-sized particles. Also disclosed is a tankless exothermic torch comprising a rod and a handle that contains a gas generating compound in the handle. The thermite torch gun does not require a tank of compressed gas. Elimination of this tank mitigates dangers and logistical burdens associated with it presence and use, without compromising operation or cutting performance. The rod may contain a high-density mixture of oxygen-releasing and/or heat-releasing chemicals. Preferably, the mixture comprises a bimodal-blend of nanometer and micrometer-sized particles in a closely-packed configuration to fill interstitial voids. The gun may contain an ignition module and power supply for initiating directed high-temperature flame jetting, and for turning it on/off/on when a solid-chemical oxygen generator is mounted in the gun.