At room temperature, a substance with a melting point of 40 Celsius is a solid.

Here's why:

* Room temperature is typically considered to be around 20-25 Celsius.

* Melting point is the temperature at which a substance transitions from a solid to a liquid.

* Since the substance's melting point is 40 Celsius, it means it will be solid at room temperature (which is lower than its melting point).