- I find the lesson interesting.
=> I am interested to the lesson.
These are possible:
I’m interested in the lesson.
I find the lesson interesting.
This is an interesting lesson.
I have great interest in this lesson.
I’m following the lesson with great interest.
‘Interesting’ is a purely descriptive state and ‘interested’ is the active state -
I am interested in something which is interesting.
The word interest takes the preposition in which may be called the ready-made preposition as in the examples provided by Torsten and Alan.