fuse, melt
熔 centers on transforming a solid into a liquid through heat: fusing metals or melting substances. The idea is heat causing a change of state.
熔 combines 火 (fire) with 容, which likely contributes the sound ヨウ and the idea of containing or shaping, suggesting melting or fusing by fire.
Fire 火 on the left and 容 (a container) on the right: picture a container being heated by fire until its contents melt and fuse together.
For ヨウ, imagine a yoyo melting in the fire: yoyo -> ヨウ, and the plastic fuses into a puddle.