The military has various high rate transient pulse applications which create unique thermal management challenges due to their high heat flux and short pulse duration. Phase change materials (PCMs) have been studied due to their ability to absorb thermal energy with minimal temperature increase. This work investigates the performance of metallic PCMs (Fields' metal (32.5Bi/51In/16.5Sn wt%) and 49Bi/18Pb/12Sn/21In wt%) acting as an integrated thermal buffer for high power 19 ms pulses. Two commercially available organic PCMs (PureTemp 29 (R) and PureTemp 58 (R)) and a dielectric gel (Sylgard 527 (R)) were used for comparison. The studied materials were deposited directly in contact with the heat-dissipating surface of a custom micro-fabricated heater chip with an embedded resistance temperature detector (RTD) for in-situ temperature measurement. PCMs were subjected to 19 ms pulses and a maximum heat flux of 338 W/cm(2) (relative to heat source area). The Bi/Pb/Sn/In PCM was able to reduce temperature rise during the pulse by 60 degrees C (63%) for 120 W and 81 degrees C (68%) for 160 W using the dielectric gel as baseline, in comparison the best performing organic PCM, PureTemp58, only reduced temperature rise by 16 degrees C (17%) and 17 degrees C (14%) for 120 W and 160 W, respectively. This supports previous assertions in the literature that metallic PCMs can be an enabling thermal protection technology for high rate transient applications. (C) 2017 Elsevier Ltd. All rights reserved.