A tin man, such as the one from The Wizard of Oz, can be relatively easy to draw if you can sketch three-dimensional shapes. Three-dimensional shapes in drawings are what make the torso of a tin man look more like a barrel, cylinder or can instead of just a big square or rectangle. Once you can draw simple cylinders, pipes, barrels and funnels, you can connect those shapes to make a tin man of your own.
Practice drawing a basic cylinder shape. A cylinder could be a can, a long tube, or anything with a round hole or surface at either end and straight sides. To draw a cylinder, draw two parallel, vertical straight lines and a flattened circle as the top. Use a straightedge as a guide if you have trouble making freehand straight, parallel lines. The bottom shape of a cylinder is also a flattened circle, but most of the circle isn't visible since it's on the bottom of the object. Instead of drawing a full circle, just draw an arc (like a smile) as if you are drawing the rounded front of a can. If you want to, you can draw the full circle and then erase the back part once you can visualise the proper layout. When you have mastered sketching a can that's upright, practice drawing other cylinders from other angles -- sideways or on an angle, for instance. Make some cylinders long and narrow, others short and wide.
Practice drawing a cone shape. A cone, when drawn, is essentially a triangle with a circle for the base. Draw a flattened circle or an oval that's wider than it is tall. Determine the centre of the circle and draw a dot straight above it where you would like the top point of the cone to be. Draw a line from the top dot connecting it to one side of the circle. Draw another line connecting the dot to the other side of the circle. You've drawn a cone! A modified cone shape is often used for a tin man's funnel hat. To make a cone into a funnel, you would "cut off" the cone before reaching the top, then add a cylinder or cone to that area. You can practice this by erasing the top part of a cone, ending it with an arc and adding a smaller, open-ended cone on top.
Practice drawing these shapes into a connected tin man body. Look at other tin man artwork, if necessary, to come up with some ideas. The arms, legs, torso and head are all cylinders and the feet can be, as well. To connect the shapes, draw rivets (circles), metal straps (rectangles) or whatever other connection devices you envision. A tin man hat is often a funnel but feel free to put your own twist on the design.
Trace the outline of your tin man once you are happy with the design, using a fine point pen. Go over some of the lines to make them thicker, if desired.
Look at other tin man drawings for reference if you don't have an idea how your tin man should look ahead of time. Look at various artistic renditions so you can see how other artists put their own twist on the tin man concept. Shading helps make shapes look more three-dimensional. A pencil is a perfect tool for shading as the pressure you give can create different shades indicating shadow and light. Practice this technique as it will be useful in many drawings. Shading can be done with pens as well. Once you have mastered drawing a tin man, try drawing him in motion, in different positions.