So lets first clarify what the difference is between free weights and resistance machines.
Free weights are typically hand held weights such as dumbbells, kettle bells and barbells. These give a true reflection of your strength, as there is no "help" during the lifts/exercises you perform.
Resistance machines are usually big and bulky, with seats, cables and weight plates. They help facilitate your ability to lift a weight and help you through your 'weak' spots during a lift.
Using free weights call on stabilising muscles to aid the larger muscles during the exercises you do, whilst the machines enable you to work specific muscle groups and isolate those areas.
What's right for you? Experienced lifters use both, depending on their goals, training intensity etc. However, we suggest that if you are new to weight training, or nursing an injury, machines are always the best place to start while you condition your body (or strengthen due to injuries), before progressing slowly to free weights to increase your strength and performance.
Following is an example of a free weight exercise that can also be performed on a machine - if you try this yourself, you will quickly realise how much easier the machine is to use - which for beginners is GREAT as it enables you to really focus on engaging your muscles and squeezing them to get the best results.
There are numerous ways to perform this exercise, but lets start with the beginner version -
the shoulder press machine.
For this one, you sit at the machine (ensuring the seat is at the correct height - keeping hands in line with the ears), set your weight (always start lighter and add weight, you don't want to injure yourself starting too heavy), then decide on your rep range (rather than get technical, I suggest reading this blog post about rep ranges, what they mean, what they do, and whats going to suit your goals, because its a debatable topic, and subject to your own interpretation, and also experimenting with different approaches).
Now let's progress to the next option -
barbell shoulder press (seated, then standing).
This is a progression from the machine, as it is a free weight, but unlike dumbbells you aren't controlling a weight with each arm independently. Given that you hold the barbell correctly, the weight is evenly distributed and still offers better balance. Although, this time you will call on more stabilising muscles as you progress through the lift.
The progression after this would be the dumbbell shoulder press (seated, then standing).
Holding a dumbbell in each hand (both the same weight), and then pressing above your head. This movement requires the most strength, coordination and stability and you are using both hands separately but simultaneously. It's important not to focus on one side more than the other otherwise you will be put off balance and increase the risk of injury. However, once you progress to this level, you will notice that even more stabilising muscles are activated throughout the movement and experience increased strength over time.
So just remember, start with the resistance machines, and move on to free weights as your body adapts. Furthermore, hire the help of an experienced Personal Trainer to monitor and assist you through these progressions. A personal trainer will also know when you're ready to tackle a more challenging movement, so you're less likely to experience any injuries.