How to use 'be of'? Why the sentence 'he is of power' is incorrect?

[Hiya Raymond]

It is of no interest to me. (of no interest=not interesting?)


Coal is of great importance to the development of industry.(of great importance=very important?)

Thanks,and please forgive my poor English,any advice and suggestions for improvement will be gratefully accepted!

 

[MikeNewYork]

It is of no interest to me. (of no interest=not interesting?)


Coal is of great importance to the development of industry.(of great importance=very important?)

Thanks,and please forgive my poor English,any advice and suggestions for improvement will be gratefully accepted!

It is simply not idiomatic English.