Can I replace the bulb in my flashlight with a high-power LED module?

Generally, no, for two important reasons.

1. The power to the LED module must be current-regulated. Almost all flashlights have no built-in current regulation, so you must modify your light to use a current-regulating driver between the batteries and the LED.
2. The LED module must be adequately cooled to prevent overheating and to ensure long life. Most incandescent bulb flashlights are not designed to provide cooling of the light source.