Joule heating is an effective method to heat solid and liquid metals in a diamond anvil cell (DAC). Here, we report the design and characterization of a pulsed Joule heating system and sample fabrication techniques for melting and electrical resistivity measurements in the DAC that includes: (a) A pulse amplifier that can drive up to 60 amps with ~ 0.5 microsecond rise time, providing more than enough current to heat metal samples with ~ 2 to 50 μm diameter to thousands of degrees kelvin at pressures from ambient to > 1 Mbar; (b) A recipe for the reproducible and precise fabrication of DAC sample, electrodes, and thermal insulation using a three-layer micro-assembly; (c) A new 5-color spectroradiometry system based on multianode photomultiplier tube technology and passive readout circuitry. Using this system we have achieved successful melting experiments of iron to >1.5 Mbar and temperatures exceeding 4000 K. Temperature measurement precision in the DAC is ~ ±30 K during single-shot heating experiments with 0.6 µs time-resolution at temperatures as low as 2000 K. We have achieved successful compression and pulsed Joule heating while maintaining a 4-point probe configuration for melting of iron metal coupled with electrical resistivity measurements Here, we will present new melting and thermal conductivity data for pure iron and discuss implications for iron thermal conductivity and Earth's core cooling rate.