my toddler is sometimes very hard to feed..

I think he's old enough to "help" in the kitchen -- mixing things, etc. Maybe if he gets involved in the preparation of the food, he'll be more inclined to eat it.

You could also try arranging the food on his plate in a fun way.

Is he still having a lot of milk? that could be hampering his hunger levels. If he is still drinking a lot of milk try cutting that down and give him other calcium rice foods, such as cheese yoghurts etc.

Never ever force anyone to finish what's on their plate. You are interfering with the person's own natural ability to determine when they are full. Over eating is what makes people fat. As long as the person is fit, healthy and has enough stamina to do what he needs to do, then nothing is wrong. What you and I believe to be "enough" are probably very different. Let your toddler decide when s/he has had enough. This way you lay the foundation for a life of healthy eating habits.

Look at all naturally slim people. They eat what they want, when they want, and stop when they are full.

one thing my mum told me when I found that my son was eating well while a little girl I care for was eating very little is a child will never let themselves starve they eat what they want when they want and will let you know if they are hungry both myself and the mother of the child I care for were a little concerned but realised that as long as the child was thriving which in her case and your child's case they are then they are obviously getting enough nourishment from what they are eating. I do use a little and often approach both to my eating habits, my son and the children I care for. One trick maybe put a really small portion on the plate and then offer seconds x

I have a four year old who is borderline underweight, she has always been small and needed her tonsil & adinoids removed at 2.5years due to them being too big. ( she had to hold her breath to swallow, lots of snoring and even apnea - which was very scarey)
she has a good apetite but quickly looses focus on eating, wanting to carry on playing instead.
She hasn't quite worked out if she just got on with it she could get playing quicker - her younger sister just gets on with it!

We now put a lot less on her plate than we used to, we found out that larger portions put her off before she started, but we always make sure we have more to offer her if she eats all she has.
We are lucky she isn't a picky eater and loves her veggies. She is not very keen on peas - but we have a "no thank you" policy with all veg we don't like so all of us (including adults) have just one desertspoonful of which ever veg we don't like, and normal portions of the rest.
We also have to restrict how much she drinks during a meal, otherwise she will fill up on that instead of eating, we try and make sure they have a drink 0.5-1hour before we eat so she isn't thirst before we start.

And we occasionally give snacks between meals mostly fruit, and I am very mean as we don't have any chocolate until after lunch
but my two are not that bothered we still have easter eggs in the fridge from last year!

Good luck, I find I am better now at judging if she is full or if she is just playing up and not focused properally.

She is just getting into age 2-3 clothes at 4.5 but she is definatly still growing and always has lots of energy just in short bursts