Is there any grammatical rule to know which verbs can (or better, must) be sometimes followed by "to"? Some examples are:
- Please explain to me why...
- She said to me that...
I'm aware I could also say "explain me", but such thing would mean something like "explain what I am" or "give an explanation of myself". However, you could never use "say me". In other cases, it seems both formats are acceptable. An example would be:
- "Show me" and "show it to me"
Is there any rule to explain this?