The butterfly can appear as a corrective pattern in a trend.
When it does, it's a two leg correction. The second leg is a false breakout of the first.
Being a harmonic, the final leg (D leg) is always the strongest.
When the butterfly serves as a corrective pattern, strong follow through can come.
In the times this works, we usually see the next swing extend 2.20 of the full range of the two leg correction (B-D legs).