Here are some examples of how to use it:
* Cacen felyn melys - A sweet yellow cake
* Mae'r siwgr yn felyn iawn - The sugar is very sweet
* Mae'r blodau hyn yn felyn eu blas - These flowers taste sweet
Keep in mind that "melys" can also be used to describe other things that are pleasant or enjoyable, not just taste. For example, you could say "Mae'r gân hon yn felyn iawn" (This song is very sweet).