I finished my diploma in metallurgy 3 years with 70% cut off - please reply am I eligible for metallurgy engineering in NIT this year?

Your marks are not that great and I don't think you have a great chance of making into the program being offered at NIT.

Yes, you can apply for lateral entry this year. But seats are very few in this college, so I would suggest you go for some other good private colleges to complete your B.Tech in metallurgical engineering. Best of luck.