Is it a myth that getting into MIT as an Indian student needs at least participation in one of the International Science Olympiads? How does MIT look upon other things like Model United Nations?

A  small proportion of international undergraduate students at MIT are International Olympiad winners or participants.  It's just one way of demonstrating that you like and are good at challenges.  It not just what you do, it's how you explain what it means to you, what it has given you etc.  MIT is going to pick just a handful of undergrads each year from India, so the bar is very, very high.  But pursue YOUR passions.  MUN is not impossible; it all depends on how you present it.  Original is good, too.

It's a myth. But it is true that statostically a large fraction of students from India at MIT are olympiad alumni. However that's nowhere close to everyone. Since you talked about Model United Nations, I wanted to mention Jesika Haria (class of 2014) who did MUN and no olympiads (although I don't know anything about the rest of her application).

See,the olympiad medals are just for strong impression,if you have a medal,they will be confident about your future performance because fetching a medal at INTERNATIONAL SCIENCE OLYMPIAD is not at all an easy task.But I think it is not compulsory to have a medal,but yes,if you are an Indian then you must secure excellent marks in SAT,IIT-JEE and your school exams because they are your primary impressions.They just need to be convinced that you are fit for MIT that's all.I hope it helps,but I think some of my words may be wrong,so inform me about them.Thanks!

Why are 4 Olympiads and class Xth boards even being compared. Prepping for Olympiads requires you to have real passion for the subject, and devotion. Class X boards, on the other hand are a joke if you are prepping for an Olympiad. So the real question should be, "how can I manage my time to get excellent result in ISOs?" My answer to that would be go one subject at a time. Start with IOAA/IAO. That is one of the easier olympiads, in the sense that you need lot less practice in terms of number of problems you need to solve to get to a level at which you are good enough to make it to nationals. I cannot tell you much about what to do for IOI IMO or IChO.

I have seen people without a single international olympiad medals get in and people with several medals rejected. It is neither necessary nor sufficient. What MIT looks for is passion and if you can demonstrate that you have pursued any field passionately and taken it to the highest level you can, then you should get in. An international olympiad medal alone is unfortunately too little in this respect.