Sir I want to join Madras Medical College in 2020. I hv joined some med college this year will I a able write NEET next year and join MMC.

Dear student,
Yes you can write NEET exam next year also and also you can shift the college
But after giving the NEET exam again you have to go through all the counselling process.
And the admission which you get through this process is into the First year. You have start your preparation again from the first year.
There is another way to get into Madras Medical college is
The medical college in which you are studying and the course which you are doing right now
Concentration more on this course and clear this year with very excellent scores and try with that score directly into second year of that college if there are any vacant seats in the second year of Madras Medical college.

All the best!

Yes you can appear in neet exam next year as neet eligibility is NEET 2020 Eligibility Criteria  Do you think you're allowed in the Exam?
ParametersNTA NEET 2020 Eligibility Criteria - Complete Detail
Qualifying Exam10+2 or equivalent from a recognized board.
Minimum Age Requirement17 years as on December 31, 2020.
Maximum Age Limit25 years (UR), 30 years (OBC/SC/ST/PwD).

Also it's very easy to predict college on careers360 by clicking on the link mentioned below its very user friendly and very helpful
https://medicine.careers360.com/neet-college-predictor

Feel free to comment if you have any doubt
Good luck