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We develop a light-emitting diode (LED) metal package consisting of a reflector integrated with a heat spreader as one body. The structure functions obtained from the thermal transient measurement reveals that the integrated structure of the metal package leads to improved thermal performance. We make significant efforts to clarify the interaction between the extracted light from the LED chip and the inside surface of the metal package. The radiant flux from the LED chip is calculated from the definition of thermal resistance and is implemented as an input parameter to predict the optical power and ray tracing. The simulated optical output power in the far-field mode is 145.3 mW, which is in good agreement with the value measured by an integrating sphere. It is shown that a large portion of the emitted light (37.12 mW) is lost by the interaction with the package surface before it reaches the far-field receiver. It is demonstrated that the angle of the first reflector cup is one of the critical design parameters in the metal package structure that we investigate. When the first reflector angle is optimized from 80° to 55° (with the second reflector angle of 50°), the optical power increases from its original value of 145.3-170.15 mW with an improved optical extraction efficiency from 75.63% to 88.57%. The ray tracing and illuminance raster charts also confirm that the improved optical performance of the metal package mainly stems from the optimization of the reflector angles.