1. **State the problem:** We need to find the equation that relates $g$, the percentage of the sculpture made of glass, to $m$, the percentage made of metal. 2. **Understand the relationship:** Since the sculpture is made of glass and metal only, their percentages must add up to 100%. 3. **Write the formula:** $$g + m = 100$$ 4. **Solve for $m$:** $$m = 100 - g$$ 5. **Interpretation:** This means the percentage of metal is the remainder when the glass percentage is subtracted from 100. **Final answer:** The correct equation is $100 - g = m$, which corresponds to option B.