Hello there

Here I'm giving you a lost of chapters which are literally do or die chapters for jee mains examination.

Mathematics-

Integrals,3-D geometry,Probability,Conic section,Trignometry,Vector algebra,Straight line,Sets relation and function,Matrices and determinant.

Physics-

Oscillation and waves,Rotational motion,Electrostatics,Atoms and nuclei,Newton's laws of motion,Current electricity,Magnetic effect of current and magnetism.

Chemistry-

Organic compouns containg nitrogen,Equllibrium,Chemical kinetics,Transition elements,S-block elements,Chemical bonding,Basic principles of organic chemistry,p-block,Coordination compound,Thermodynamics.

You can refer this link also for chapter wise weightage and further more details:

https://engineering.careers360.com/articles/jee-main-syllabus-weightage

I hope it helps you!

Good luck!