Les pilier as they are called in France; props are the pillars, the anchors, the foundations, or indeed any number of metaphors and clichés of your choosing. All of which are similarly designed to assert that propsare; out in front of the team, standing firm, the first line into battle.
Well of course the clue is in the name, they make up two thirds of the Front Row. Big, strong, square men. Heavy, but worth their weight in gold. Their importance to the team in set pieces alone means that Front Row players are amongst the highest earners in professional teams, behind only the goal kickers. The intricacies of the scrum are what differentiates the Tight Head Prop form the Loose Head, with very few players being able to play both positions.
Stereotypically not the sharpest tools in the box, their fearlessness can often be misconstrued as lack of intelligence by those who watch on, as they continue to throw themselves head first at the opposition to win the ball for their team. Whether it be through ignorance of danger or sheer bravery, dominance at the scrum can win matches or lose them. However, the job of the modern day Prop reaches far beyond the set piece, they must be Ball Carriers and Ball Winners, Tacklers and Tackle Breakers. If you want to be an outstanding Prop, you must spend as much time out on the field practising skills as you do in the gym pumping iron. Especially true in lower divisions where there are traditionally more knock ons and scrums, props have a huge impact on the outcome of matches. Numbers 1 and 3 they are the first names down on the team sheet, they lead the team out and the rest follow.
Without the Pillars your team will be propping up the bottom of the league no matter who you have behind them.