Problem with one comparetive...

Hello people, today I want to do one ask a question...Is this correct: "more light than"??? I think that is the best way to say it is "lighter" but is it okay to say good "more light than"... in some places, I have read the expresion "more fat than" because of and so can I say "more light than". Thanks.

To form the comparative of adjectives in English we follow two conventions:

1) Short adjective add -er to the adjective

2) Long adjectives use "more" + adjective

One-syllable adjective almost always add -er:  lighter, hotter, bigger, smarter, smaller, fatter, colder, etc.

Some two-syllable adjective can go either way: 

quiet → quieter/more quiet
clever → cleverer/more clever
narrow → narrower/more narrow
simple → simpler/more simple

Problem with one comparetive...

Hello people, today I want to do one question...Is correct "more light than"??? I think that is the best "lighter" but is good "more light than"... in some place, I have read the expresion "more fat than" because of I can say "more light than". thanks.

I would say that lighter than is better in this context.   Example: The color yellow is lighter than the color blue." 

As for the expression "more fat than"  it might be better to say "fatter than"  Example: Tom is fatter than Jim. 

Good luck in improving your English!