Question: I'm doing a speech & want to say "I don't often get given a platform like this" 

I've been trying to find the word 'platform', but they only thing that comes up is the term 'platform' in terms of a train station. (i.e. the noun)

Is there a Japanese equivalent to the 'platform' we use in the metaphorical sense in English? 

Thanks!

Answer: 
「舞台{ぶたい}」 would be a fairly good word choice if you are referring to the opportunity to give a speech someplace.
Metaphors don't always translate well. You might just be more specific about what you mean by "platform". For example, is it the opportunity to talk to so many people already working in your planned career field? Or the chance to speak directly to potential or current customers? 
If you just mean, "it's an honor/pleasure to be here" you could say something like 今日は、会場の皆様にお呼び頂いて、光栄です