Hard to say which species of maple this is. Where did it come from? Where (at least generally) in the world are you located. Is it a seedling from somewhere out in the back yard? A nursery? Should we be looking at possible native USA maples? Or one of the European maples?
Assuming you are in the USA, my first guess would be "Norway maple", Acer pseudoplatanus, a European species that has become a weed tree in the USA and is ubiquitous in urban and suburban back yards. If you cut a leaf off, the leaf petiole should bleed a milky white sap. The USA native sugar maple Acer saccharum, will bleed a clear, colorless sap.
But without more information, it is hard to say.
By the way, this forum has been rather sleepy lately, but when someone finally answers, the replies tend to be high in good information, as opposed to Bonsai Nut, where you will get many replies per hour, and half will be nonsense or sometimes just plain wrong or misleading. However, I do like BNut, but you do have to double check information in replies, especially from certain posters.
Everything on the internet is true, right? Check replies here too, though generally this forum is pretty good.