On a resistor with four colour bands, what do the first three colour bands indicate?

A standard four-band resistor uses its colour bands to communicate its electrical specifications. The first three bands work together to indicate the nominal resistance value in ohms. Specifically, the first two bands represent the first two significant digits of the value, and the third band is the decimal multiplier (the number of zeros to append to the digits). Other characteristics like power rating or physical material are not indicated by these bands; power rating is typically determined by the physical size and shape of the resistor.