Warm the tomato soup in a saucepan over medium-low heat, stirring occasionally. Keep it warm while you make the sandwiches.
Lay out the bread and butter one side of each slice. Place four slices butter-side down, then add a slice of cheddar, two pieces of smoked meatloaf, and another slice of cheddar to each. Top with the remaining bread, butter-side up.
Heat a large skillet over medium-low heat. Cook the sandwiches in batches, if needed, for 3 to 4 minutes per side. Press gently with a spatula and turn them when the bottoms are golden brown.
Continue cooking until the bread is crisp and the cheddar has melted. If the bread browns before the cheese melts, lower the heat and cover the skillet briefly.
Cut each sandwich in half and serve warm with the tomato soup alongside for dipping.